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Phosphorescent metal complexes find widespread application in organic light-emitting diodes (OLEDs), with iridium(III) complexes being particularly favored for their superior performance. Owing to the flexible modifications of both main and auxiliary ligands, the photophysical properties of iridium(III) complexes can be finely tuned. In this study, two red neutral iridium(III) complexes, designated as Ir1 and Ir2 , are successfully synthesized and characterized. Various auxiliary ligands including acetylacetone and 2-picolinic acid are employed in combination with 1-(6-methoxynaphthalene-2-yl)isoquinoline as the cyclometalating ligand. Both complexes exhibit red emission, with Ir1 emitting at 631 nm and Ir2 at 615 nm. Furthermore, they demonstrated good solubility in common organic solvents, facilitating device fabrication via solution methods. Electroluminescent (EL) devices based on complexes Ir1 and Ir2 are further prepared using spin-coating method, achieving maximum external quantum efficiencies (EQEs) of 3.30 % and 4.52 %, respectively, and both devices exhibited bright red EL with CIE coordinates of (0.68, 0.32) and (0.66, 0.34), which were very close to the standard red coordinates of (0.67, 0.33). [Display omitted] • Two neutral red iridium(III) complexes were designed using naphthalenyl isoquinoline as the main ligand. • Solution-processed OLEDs were prepared to investigate the electroluminescence of these complexes. • The Ir2-based device demonstrated the best electroluminescent performance with an external quantum efficiency of 4.52 %. [ABSTRACT FROM AUTHOR]

Solid-state light-emitting electrochemical cells (LECs) offer promising benefits, including simple device architecture, low operating voltage, and insensitivity to electrode work functions. These advantages make them highly suitable for low-cost display and lighting applications, with significant potential for widespread adoption. However, great challenges remain in realizing stable and efficient white LECs. In this work, the blue LECs integrated with red or yellow/red quantum-dot (QD) color conversion layers (CCLs) are shown to achieve efficient and stable white emissions. When the blue LECs are combined with red QD CCLs, they achieve an external quantum efficiency (EQE) exceeding 20 % at a low current density of 0.003 mA cm−2. Alternatively, the blue LECs integrated with yellow/red QD CCLs deliver white emissions with a low CCT <2500 K and a high CRI up to 93 while the peak EQE at a low current density of 0.005 mA cm−2 still remains high (>16 %). The data effectively showcase that efficient and stable white emission can be achieved through partial energy down-conversion from the blue LECs to the QD CCLs, and the proposed white light sources are potential candidates for lighting applications. [Display omitted] • White light sources using blue LECs and red or yellow/red QD color conversion layers. • Peak external quantum efficiencies of the proposed devices are higher than 20 %. • The white EL spectra are stable in a wide range of operating current. [ABSTRACT FROM AUTHOR]

Herein, we designed pure exciplex emission, white organic light emitting diodes (WOLED) with simple single-emitting-layer (S-EML) structure through a ternary donor/acceptor system. Three kinds of donor/acceptor materials in one emitting layer of mCP:PO-T2T(1:1): x% m -MTDATA or TAPC:TPBi (1:1): x% PO-T2T could produce the white emission with high energy blue and low energy orange exciplex emission. As a result, the pure exciplex WOLED based on S-EML structure were achieved successfully with the optimized maximum luminance of 4047 cd m−2, current efficiency of 10.26 cd A−1, power efficiency of 10.57 lm W−1 and EQE of 3.4% with the two complementary color exciplex emissions. To our knowledge, this is the first time to achieve a S-EML structure pure exciplex emission WOLED. The efficient energy transfer from high energy exciplex to low energy exciplex could be also observed in this ternary system. [Display omitted] • The S-EML structure WOLED based pure exciplex emission through ternary donor/acceptor system is realized. • The efficient energy transfer from high energy exciplex to low energy exciplex could be observed. • The optimized maximum luminance of 4047 cd m−2, CE of 10.26 cd A−1, PE of 10.57 lm W−1 and EQE of 3.4% are obtained. [ABSTRACT FROM AUTHOR]

In this study, an amphiphilic organic fluorescent molecule (denoted by BCPB) was employed as a ratiometric fluorescent probe for the detection of human serum albumin (HSA). In an aqueous solution, the micellar assemblies of BCPB showed a strong excimer emission at 660 nm. The presence of HSA can induce the disassembly of BCPB aggregates and reassemble with HSA to form BCPB-HSA complexes, resulting in a ratio change in the fluorescence emission of BCPB at 540 nm (monomer) and 660 nm (aggregate). Accordingly, the fluorescence color also undergoes a visually recognizable change from red to green. As a ratiometric fluorescence probe of HSA, BCPB has a fast response (<5 s), low limit of detection (8.3 nmol L−1, S / N = 3), good selectivity, and strong anti-interference ability. Finally, BCPB was loaded into the hydrogel to prepare a portable hydrogel kit, which successfully realized the in situ visual detection of HSA in an aqueous solution and human serum. [Display omitted] • A ratiometric fluorescent probe was constructed by supramolecular self-assembly. • The probe showed excellent sensitivity, selectivity and anti-interference ability. • A hydrogel kit was applied for quantitative analysis of HSA in human serum. [ABSTRACT FROM AUTHOR]

Donor-acceptor systems exhibiting exciplex luminescence attract much attention due to the wide prospects for their application in the field of OLEDs, nonlinear optics and lasers. Difluoroboron β-diketonates (BF 2 bdks) are a well-known class of organic dyes, which are able to form effective exciplex fluorescence, but this process has not received due attention for practical application. Strong donor-acceptor interaction in polyvinylcarbazole (donor) and BF 2 bdks derivatives (acceptor) binary system induces deeply red-shifted emission of charge-transfer complexes and exciplexes with a large bathochromic shift up to ∼170 nm relative to conventional monomeric luminescence. The results of quantum chemistry simulation are in agreement with the experiment data. Luminescence color tuning of the film are capable by the dye concentration, the donor-acceptor properties of the dye substituents and even the excitation wavelength. White light broad spectrum of a dual luminescence of the investigated binary systems has CIE chromaticity coordinates (0.35; 0.33) close to the standard neutral white light CIE coordinates (0.33; 0.33). This study will facilitate photophysical research and industrial applications of donor-acceptor binary systems based on polymer materials. [Display omitted] • Strong donor-acceptor interaction of polyvinylcarbazole and BF 2 bdks was revealed. • Charge-transfer complexes and exciplexes between BF 2 bdks and carbazolyl groups form. • Experiment data are in agreement with the results of quantum chemistry simulation. • Acceptor properties of substituents of BF 2 bdks affect the charge separation process. • Luminescence color tuning of the PVK film doped with BF 2 bdks is possible. [ABSTRACT FROM AUTHOR]

Excimer materials are frequently applied to organic chemistry, optoelectronic devices and stimulus response. Specific research on the entire process of excimer generation in solid materials, as well as the intricate mechanism of piezochromic luminescence based on excimer, are still absent and need to be examined in-depth through comprehensive experiments. Therefore, we designed an anthracene-based molecule CZPAN , which adopts no overlap area between anthracene molecules in its crystal at ambient conditions, to investigate the piezochromic luminescence behavior and expect the anthracene group to form excimers under high-pressure stimulation. As pressure increases, CZPAN gradually changes from blue monomer luminescence to green excimer luminescence accompanied with the considerably red-shifted emission spectra, and exhibits a discontinuity of fluorescence quenching during the formation of excimers (in the pressure range of 5.3–6.6 GPa). Moreover, the pressure relief process is fully reversible. This study presents abundant piezochromic luminescence of CZPAN and proves that the formation of excimers requires a certain overlap area between molecules. Pursuing the appropriate strength of π–π interactions will thus be the focus of future research on excimer materials of high luminescence efficiency, so that excimers can be better applied in sensors and imaging devices. [Display omitted] • There are no overlap areas between anthracene molecules in the designed crystal at ambient conditions. • High pressure induces the formation of excimers. • The designed crystal shows abundant phenomena of piezochromic luminescence during compression. • High luminescence efficiency of excimers requires the appropriate strength of π–π interactions. [ABSTRACT FROM AUTHOR]

We synthesized two novel Pt(Ⅱ) β-diketonate compounds, 2′,6′-dimethoxy-4- tert -butyl-2,3′-bipyridinato-N,C4′)platinum(Ⅱ)(acetylactonate-O,O) (1) and 2′,6′-dimethoxy-4-trimethylsilyl-2,3′-bipyridinato-N,C4′)platinum(Ⅱ)(acetylactonate-O,O) (2), to develop blue phosphorescent compounds and systematically investigated their photoluminescent and electroluminescent characteristics. The compounds 1 and 2 exhibited bright sky-blue phosphorescence, with a phosphorescence maximum (λ max) at 465 nm and 475 nm, respectively. The luminescence quantum yields were found to be 0.63 for 1 and 0.93 for 2. At high concentrations, both compounds exhibited bright red emission originating from the formation of excimer. However, compound 2 , due to effective intermolecular interactions, exhibited a more red-shifted emission than compound 1 at the same concentration. For fabricating phosphorescent organic light-emitting diodes, the compounds 1 and 2 were used as dopants, and a 50:50 mixture of 3′-di(9H-carbazol-9-yl)-1,1′-biphenyl:9-(3′-carbazol-9-yl-5-cyano-biphenyl-3-yl)-9H-carbazole-3-carbonitrile was used as the mixed host. When doped with 20 wt% of compound 2 , the electroluminescent device exhibited the best performance, achieving an external quantum efficiency (EQE) of 13.7% at 100 cd/m2 and current efficiency of 35.5 cd A−1. Remarkably, the single-doped compound 2 -based device achieved emission with Commission Internationale de L'Eclairage coordinates (x, y) of (0.40, 0.48). To the best of our knowledge, this is one of the highest performing single-doped white organic light-emitting diodes. • Two novel cyclometallated Pt(II) β-diketonate compounds were synthesized. • 4-Position of a N-coordinating ligand pyridine ring was substituted by TMS or t Bu. • Substituents affected photophysical and electroluminescent properties differently. • High-performance OLED was prepared by doping the Pt(II) compounds in a mixed host. [ABSTRACT FROM AUTHOR]

Abstract To provide high exciton utilization in organic light emitting diodes, phthalimide derivatives were designed and synthesized as exciplex-forming materials. Due to high triplet levels (2.92–3.11 eV) and ionization potentials (7.18–7.29 eV), the developed phthalimide derivatives were found to be not only appropriate accepting materials for the formation of different color exciplexes but also as bifunctional materials with a satisfactory hole and exciton-blocking abilities. Solid-state blends of the synthesized phthalimides as acceptors and a carbazole containing donors showed exciplex emission. Bimolecular blends exhibited multicolor exciplex emission which covered a visible spectrum from sky-blue to red colors, depending on the donor used. However, the photoluminescence quantum efficiencies of the studied exciplex-forming systems were found to be sensitive to the molecular design of the phthalimides. Acceptor with para-substituted phthalimide showed better exciplex-forming properties in comparison to other compounds. Exciplex-forming blend of (2-(4-benzoylphenyl)isoindoline-1,3-dione) as an acceptor and 1,3-di(9H-carbazol-9-yl)benzene (mCP) as a donor showed the most efficient sky-blue emission with small singlet-triplet splitting (0.06 ± 0.03eV). Such exciplex-forming molecular mixture was implemented as the light-emitting material in the sky-blue organic light emitting diodes which showed the brightness of 2500 cd m−2 and maximum external quantum efficiency of 2.9% due to the employment of both singlet and triplet excitons. Graphical abstract Image 1 Highlights • Five novel phthalimide based acceptors with high triplet levels (2.92–3.11 eV). • Exciplex forming properties of acceptors were sensitive to the molecules design. • A para-substituted phthalimide-benzophenone in blend with donor showed sky-blue exciplex emission with ΔE ST gap ~ 0.06eV. [ABSTRACT FROM AUTHOR]

Multiresonance thermally activated delayed fluorescence (MR-TADF) materials have attracted wide attention due to their large radiation rate constant (k r) and high color purity. Attaching additional electron donor or acceptor was established as an effective strategy to optimize the optoelectronic parameters of MR-TADF emitters, such as the reverse intersystem crossing rate constant (k RISC). However, these is no report that both the MR and twisted intramolecular charge transfer (TICT) excited states can be detected simultaneously from a single molecule yet. Herein, a group of MR-TADF emitters BNCz-SAF, BNCz-DMAC and BNCz-PXZ are designed and synthesized through introducing different donor, spiroacridine (SAF), acridine (DMAC) and phenoxazine (PXZ), at the para-site of the boron atom of a famous MR core BNCz. All these three emitters maintained intrinsically excellent properties of MR-TADF molecules with high k r over 108 s−1 and high k RISC over 105 s−1. Interestingly, with gradually increasing the donor strength to PXZ, dual emissions from the MR core and the CT excited state between PXZ and BNCz moieties are detected simultaneously for BNCz-PXZ in either strong polar solvents or doped film in highly polar host, both of which are confirmed as the TADF with the lifetimes of about 4 μs. Independent of the host, the organic light-emitting diodes (OLEDs) of BNCz-SAF and BNCz-DMAC exhibited sky-blue electroluminescence with high external quantum efficiencies (EQE max) of 25.3% and 23.8% and narrow full widths at half maximum (FWHM) of 23–25 nm. In contrast, BNCz-PXZ exhibited a single-band (482 nm) sky-blue EL in mCBP host with EQE max of 20.9%, while exhibited dual-band EL at 484 and 548 nm from MR and CT states in higher polar host DPEPO, realizing a warm white emission with CIE (0.31, 0.48) and EQE max of 16.4%. For the first time both the short-range CT (i.e. MR) and long-range CT (i.e. TICT) excited states are experimently detected and confirmed simultaneously from a donor-modified B,N-based polycyclic hydrocarbon skeleton, which may be a potential strategy to bulid up broad-spectra or white emission. Dual TADF was experimentally confirmed from the donor modified multiresonance TADF framework through tuning the donor strength, from the coexistent short-range charge transfer (CT) state of the MR core and the long-range twisted intramolecular CT state between MR core and the PXZ donor. Warm white OLED was realized with CIE (0.31, 0.48) and EQE of 16.4% when BNCz-PXZ was doped in polar host. [Display omitted] • Three MR-TADF emitters were developed by introducing different donors into the BNCz framework. • Both high k r over 108 s−1 and high k RISC over 105 s−1 were achieved for all these emitters. • Weak donor modified emitters exhibited single-band blue emission, resulting in EQE of 25.3% and 23.8% in OLEDs. • Dual TADF was detected for strong donor based BNCz-PXZ, from SRCT state of the MR core and the long-range TICT state. • When DPEPO was used as host for BNCz-PXZ, single-molecule warm white emission was achieved in its OLED with EQE of 16.4%. [ABSTRACT FROM AUTHOR]

Cyclosiloxanes bearing 1-naphthyl and 5-substituted naphthyl groups have been prepared from the corresponding silanediols with bases such as triethylamine and 1,8-diazabicyclo[5.4.0]undec-7ene (DBU) in moderate yields. The selectivity for the synthesis of cyclotrisiloxanes [-SiAr 2 -O-] 3 and cyclotetrasiloxanes [-SiAr 2 -O-] 4 can be controlled by the substituents on the naphthyl rings and the strength of the base. A less reactive silanediol by introducing of electron-donating groups such as dimethylamino groups gave kinetically controlled cyclotrisiloxane. Di(1-naphthyl)silanediol was also found to give the corresponding cyclotrisiloxane with triethylamine. Meanwhile, reactive silanediol bearing electron-withdrawing groups afforded the corresponding thermodynamically stable cyclotetrasiloxane even in the presence of triethylamine. Strong base such as DBU promoted the rearrangement from cyclotrisiloxane to cyclotetrasiloxane by HPLC analysis, therefore the latter product was obtained as the main product. The photophysical properties of cyclotrisiloxanes 4b (Ar = 1-naphthyl) and 4c (Ar = 1-(5- N , N -dimethylaminonaphthlyl)), and cyclotetrasiloxanes 5a (Ar = 1-(5-cyanonaphthyl)) and 5b (Ar = 1-naphthyl) were carried out in different organic solvents. Cyclotrisiloxane 4b showed both monomer and excimer emission. Cyclotetrasiloxanes 5a and 5b showed characteristic excimer emission due to the fully overlapping naphthyl groups on the vicinal silicon atoms in the ground state from X-ray and theoretical calculations. Cyclotrisiloxane 4c showed broad emission and high quantum yield. The emission wavelength depended on the solvent polarity due to the ICT of the naphthyl groups. The solubility of the cyclosiloxanes was improved compared to previously reported cyclosiloxanes having 1-pyrenyl groups. • Selective synthesis of cyclosiloxanes with substituted naphthyl groups. • Mechanism of the selectivity for the synthesis of the cyclosiloxanes. • Structural analysis by NMR, MS, X-ray, and DFT calculations. • Photophysical properties of the cyclosiloxanes. • Excimer and ICT emission of the cyclosiloxanes. [ABSTRACT FROM AUTHOR]

In this work, a novel dual-emission compound (PTZ-CO-PNA) with the asymmetric D-A-D' structure was designed and synthesized, in which one side of carbonyl benzene was directly connected to phenothiazine unit, and the other side was N -phenyl-2-naphthylamine moiety. In the monomolecular state, PTZ-CO-PNA exhibited a single emission originated from the mixed charge transfer state and local excited state. In the different aggregation state (crystal, ground powder, thermally treated solid), PTZ-CO-PNA displayed a stable dual emission located at about 435 and 523 nm with the CIE coordinates of (0.27, 0.39), (0.28, 0.40), (0.29, 0.42) and (0.31, 0.42), respectively, closed to the white light emission. Importantly, both emissions in crystal exhibited long lifetimes (>50 ms) and the quantum yield was 10%. Moreover, in the crystal, PTZ-CO-PNA had relatively tight stacking with the intermolecular interaction of the C–H ... π, S ... π and π ... π bonds and exhibited a large steric hindrance between phenothiazine unit and carbonyl benzene. The above-mentioned results proved that the dual emissions were derived from the monomolecular and aggregation states in the solid. Finally, PTZ-CO-PNA as the emitter could be used to prepare the near-white OLED that the doped device showed a greenish-white light emission with a CIE coordinate of (0.260, 0.326). [Display omitted] • A dual emission compound PTZ-CO-PNA with a twisted and asymmetrically D-A-D′ structure was synthesized. • The compound exhibited relatively stable dual emissions at 441 and 523 nm in the different aggregate states. • PTZ-CO-PNA exhibited a greenish-white light emission with a CIE coordinate of (0.260, 0.326) in the doped OLED. [ABSTRACT FROM AUTHOR]

The development of organic single-molecule multiple photoluminescence compounds hold a great promise for advanced opt-electronic devices, optical probes and temperature sensors. The pyrenyl-substituted o -carborane, CSP and CDP , were obtained via a modified nickel-catalyzed cross-coupling reaction in satisfactory yields. Based on variety of spectroscopic measurements, it was found that the CSP and CDP exhibit multifunctional luminescent properties, such as dual emissions as well as thermochromic luminescence between orange and blue for CSP , ternary species emissions for CDP , and aggregation induced emission (AIE) and AIE enhancements (AIEE) properties for both. The origination of the multiple photoluminescence attributes was investigated deeply. We demonstrated that the multiple photoluminescence in the pyrenyl-substituted o -carborane rose from the electronic interaction between pyrenyl and o -carboranyl leading to the formation of ICT state, and the mono-molecular excimer emission attributed to the interaction between the conformational of two “face−to−face” pyrene chromophores. In addition, clear thermochromic luminescence properties were caused by ICT at room temperature and excimer formation at 77 K in the solid state. The results are useful as a guideline for designing luminescent solid materials with multiple photoluminescence and thermochromic luminescence properties. [ABSTRACT FROM AUTHOR]

Two cyano-substituted spiro[fluorine-9,9′-xanthene] (SFX) derivatives, 2-carbonitrile-spiro[fluorene-9,9′-xanthene] (CNSFX) and 2,7-dicarbonitrile-spiro[fluorene-9,9′-xanthene] (DCNSFX) were conveniently prepared as electron acceptors to combine with tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as electron donor to form exciplex emitters, respectively. Favorable exciplex-TADF was successfully achieved with photoluminescence quantum yield of 31% and electroluminescence efficiency of 8.2 cd A −1 in TCTA:DCNSFX, which possesses increases of 1.1 and 3.3 times than those (15% and 1.9 cd A −1 ) of TCTA:CNSFX, respectively. The relatively favorable performance of TCTA:DCNSFX is related to the stronger electron-accepting ability through dicyano-substitution and larger driving force in the exciplex emission. These appealing results reveal that the dicyano-substituted SFX derivative opens interesting perspectives for developing favorable exciplex-TADF organic light-emitting diodes in the future. [ABSTRACT FROM AUTHOR]

A new luminescent ambipolar semiconductor consisting of 1,8-naphthalimide as an electron-accepting moiety and carbazole as an electron-donating moiety has been synthesized and characterized. The synthesized compound as ambipolar semiconductor has been investigated by using density functional theory calculations coupled with the charge-hopping model and the time-of-flight experimental method. The time-of-flight hole and electron drift mobilities in the synthesized material's layer approached about 10 −4 cm 2 V −1 s −1 at high electric fields. The exciplex complex is stabilized by the intermolecular hydrogen bond and electron donor-acceptor interactions. The energy of interactions between the molecules in the exciplex complex has been estimated to be about −100 kJ mol −1 by DFT. Non-doped emissive layer organic light-emitting diode (OLED) using the synthesized compound as an emitter exhibited an orange color emission with the Commission International de L'Eclairage chromaticity coordinates of (0.47, 0.49). [ABSTRACT FROM AUTHOR]

We have previously reported that crystalline samples of 1-acetylaminopyrene (AAPy), 1-octanoylaminopyrene (OAPy), and 1-stearoylaminopyrene (SAPy) exhibited mechanochromic luminescence. In the present study, we have found that these 1-alkanoylaminopyrenes adsorbed onto cellulose papers also exhibited mechanochromic luminescence; however, their behaviors were essentially different from those observed for their crystalline samples. In addition, these cellulose papers were found to exhibit reversible emission color change upon alternate exposure to ethanol and water vapors. It was suggested that 1-alkanoylaminopyrene molecules were dispersed in the paper without aggregation or crystallization and that intermolecular distance of 1-alkanoylaminopyrenes in the paper was reduced by either mechanical stress or exposure to ethanol vapor, resulting in increasing the sites where excimers could be formed and/or in enhancing the efficiencies of energy migration to reach the excimer sites. [ABSTRACT FROM AUTHOR]

Arylfluorenyl-substituted triphenylamines were prepared by acid promoted Friedel-Crafts-type substitution reaction. The synthesized compounds were found to be capable of glass formation with glass transition temperatures above 152 °C. The ionization potentials of the layers of the derivatives were found to be in the range of 5.25–5.41 eV. Time-of-flight hole and electron drift mobility values of the layer of tris[3-methoxy-4-(9-phenyl-9-fluorenyl)phenyl]amine well exceeded 10 −3 cm 2 /V at high electric fields at room temperature. The results obtained by means of density functional theory calculations were used to discuss on the charge-transporting and optical properties of the compounds. Deep blue exciplexes formed by the newly synthesized arylfluorenyl-substituted triphenylamines and the known electron-transporting materials 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) or 4,7-diphenyl-1,10-phenanthroline (Bphen) were discovered and studied. Based on these exciplexes, we propose an original structure of cold white OLED with CIE chromaticity coordinates ranging from (0.286, 0.378) to (0.24, 0.29) depending on applied voltages. Electroluminescence spectra of cold white OLED consist of deep blue and green emissions which originate from bulk and interface. The origin of green emission is thermally activated delayed fluorescence (TADF) from exciplex formed between 4,4′,4″-tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA) and Bphen. Based on the newly discovered exciplex emitters, deep blue OLED with the electroluminescence maximum at 428 nm and with CIE chromaticity coordinates of (0.179; 0.104) was fabricated. The cold white and deep blue devices showed external quantum efficiencies of 2.55% and 1.2%, respectively. [ABSTRACT FROM AUTHOR]

Four carbazol-9-yl and diphenylamino substituted 9-ethylcarbazole derivatives having cyano groups in the substituents were synthesized and characterized by the experimental and theoretical tools. Thermal, optical, photophysical and electrochemical properties were studied. The derivatives exhibited moderate thermal stability with 5% weight loss temperatures exceeding 300 °C. All the derivatives were found to be capable of glass formation with glass transition temperatures ranging from 77 to 111 °C. The optical band gaps of the solid samples were 2.84–3.38 eV. One of the derivatives was used for the preparation of blue non-doped emitting layer and as exciplex forming material for the fabrication of blue and yellow organic light emitting diodes with CIE color coordinates of (0.17, 0.28) and (0.40, 0.52), respectively. The electroluminescence of the yellow exciplexes based device resulted from the overlapping of sky blue bulk emission with photoluminescence quantum efficiency of 43.8% and orange interface exciplex emission with the efficiency of 3.84%. The fluorescent non-doped blue OLED exhibited maximum luminance of 2515 cd/m 2 and external quantum efficiency reaching of 2%, while the yellow exciplex OLED exploiting the effect of thermally activated delayed fluorescence had maximum luminance of 6260 cd/m 2 and external quantum efficiency of 5.8%. In addition, sky-blue and orange OLEDs with only one exciplex-based emitter were fabricated showing external quantum efficiencies of 4.2 and 3.2%, respectively. This work provides background for the fabrication of efficient OLEDs combining advantages of both interface and bulk exciplex emissions (maximal internal quantum efficiency of 100%, provision of exelent charge balance in emitting layer, formation of the “active” planar pn heterojunctions). [ABSTRACT FROM AUTHOR]

The ratio of locally excited (LE) and charge transfer (CT) components plays a key role in harvesting the "hot" triplet excitons through high-lying reverse intersystem crossing (hRISC) in organic light-emitting materials. Herein, two blue carbazole derivative isomers 2,7-Cz(DOFCP) 2 and 3,6-Cz(DOFCP) 2 were designed with A-π-D-π-A structures. The localized π-conjugation and intramolecular charge transfer components ratio was rationally varied by the substitute position of 9,9-dioctylfluorenyl (DOF) π-bridge on the carbazolyl donor unit. Both of the emitters exhibited hybridized local and charge transfer (HLCT) characteristics, and 2,7-Cz(DOFCP) 2 with prolonged localized π-conjugation nature realized a smaller energy splitting (Δ E S2-T3) and higher fluorescence quantum yield. The OLEDs based on the emitters achieved deep blue and nearly standard blue electroluminescence with the CIE coordinates of (0.153, 0.063) and (0.153, 0.091), and maximum EQE s of 5.57% and 7.37% that was beyond the conventional fluorescence devices, respectively. This work would provide insights for promoting the luminescence performance of the HLCT molecules by adjusting the LE/CT proportion in the excited states. • The ratio of LE/CT was regulated by varing the substitute site on carbazole unit. • Both synthesized carbazole derivatives are HLCT molecules. • The compound with 2,7-substitute exhibits deep blue emission and the highest PLQY. • The compound with 3,6-substitute exhibits pure blue emission and the best EQE. [ABSTRACT FROM AUTHOR]

Two fluorescent emitters based imidazole and carbazole were synthesized for deep blue emission organic light-emitting diodes (OLED) with non-doped structure. The photophysical, thermal and electrochemical properties are investigated with high decomposition temperature up to 391 and 380 °C, and strong deep blue emission. Single carrier devices were also fabricated to show that two compounds have good bipolar carrier transport characteristic. The non-doped fluorescent OLED devices using the two compounds as emitting layers are designed among which the devices achieved the maximum external quantum efficiency of 1.66% and 1.56%, respectively. Besides, the deep blue emission peak of 412 nm with Commission Internationale de l'Eclairage (CIE) coordinate of (0.16, 0.04), and 420 nm with CIE coordinate of (0.16, 0.05) were also realized. The small CIEy value of 0.04 and 0.05 obtained in this work are very significant for high color purity full-color display, which is also among the best CIEy value results ever reported as deep blue bipolar emitters. • Two fluorescent emitters based imidazole and carbazole were synthesized for deep blue OLED with non-doped structure. • The OLED achieved the maximum EQE of 1.66% and 1.56%, with deep blue emission peak of 412 and 420 nm, respectively. • The small CIEy value of 0.04 and 0.05 is among the best CIEy value results ever reported as deep blue emitters. [ABSTRACT FROM AUTHOR]

The design, synthesis, and characterization of a series of novel Y-shaped push-pull compounds based on the quinoxaline and pyrido[2,3- b ]pyrazine moieties as electron acceptors, 1,4-phenylene rings as spacers, and pyrene units as electron donors was carried out. Their structural, photophysical, solvatochromic, aggregation, acidofluorochromic, moisture sensing and thermal characteristics were investigated. It was observed that the substitution of an electron withdrawing group (EWG) on the quinoxaline moiety led to red shifts in the absorption and emission spectra due to enhanced intramolecular charge transfer (ICT). Crystal structure of 3a showed twisted structure with herringbone packing arrangement and intermolecular π-π stacking of pyrene units. Compounds 3a-c displayed aggregation induced excimer emission in aggregated states in THF-water mixtures due to intermolecular π-π interactions among pyrene units. The concentration dependent studies of 3a-d showed monomer/excimer conversion at higher concentrations in THF solvent. The excited lifetime analysis revealed a biexponential decay at lower concentrations with a major contribution from monomeric species while at higher concentrations, a triexponential decay was observed with a major contribution from the excimeric species. The lifetimes for the monomeric species (2.9–3.3 ns) were found to be higher than the excimeric species (1.3–2.6 ns). These compounds displayed reversible acidofluorochromism, in solution and in solid state, with TFA followed by subsequent treatment with TEA. Compounds were also able to detect up to 0.005 v/v % moisture in THF solvent through TICT mechanism. Filter paper strips coated with these compounds were able to detect TFA vapors and moisture, which shows the practical application of these compounds. [Display omitted] • Design, synthesis, and characterization of novel Y-shaped pyrene substituted quinoxaline/pyridopyrazine derivatives. • Aggregation induced excimer emission in aggregated states (THF: H 2 O). • Reversible acidochromism in solution as well as solid state. • TICT-induced moisture detection in organic solvent THF. • Fabrication of paper strips for volatile acid and moisture detection. [ABSTRACT FROM AUTHOR]

Molecules with hybrid local charge transfer (HLCT) state can theoretically realize 100% exciton utilization by using high energy level triplet excitons to generate singlet excitons through reverse intersystem crossing, and thus has attracted attention. Because it is difficult to obtain HLCT molecules with both short-wavelength emission and high exciton utilization, it is challenging to develop high-performance pure blue organic light-emitting diodes (OLEDs). In this study, a series of novel D-π-A blue emitters (CZ-Ph-BTOBF , DCZ-Ph-BTOBF and SAF-Ph-BTOBF) with carbazolyl or acridinyl group as a donor, benzo [4,5]thieno- S , S -dioxide-[3,2- b ]benzofuran (BTOBF) as an acceptor, and phenyl group as a π bridge are designed and synthesized. These emitters exhibit good thermal, morphological stability and HLCT excited-state characteristics. OLEDs using CZ-Ph-BTOBF efficiently emits pure blue light (472 nm, CIEx,y = 0.15, 0.17) with full width at half maximum (FWHM) of 65 nm and maximum external quantum efficiency (EQE) of 6.85%. The visible bright blue emission is corroborated by the remarkably high photoluminescent quantum yield up to 92% in doped thin films. OLEDs of DCZ-Ph-BTOBF also exhibit pure blue emission with enhanced color purity (CIEx,y = 0.15, 0.11) and narrow emission peaks (FWHM = 64 nm). In conclusion, by adding a phenyl π bridge between the donor and acceptor groups, triplet excitons can be utilized through HLCT excited states and thus the electroluminescence efficiency can be improved. These results suggest that the rationally designed BTOBF based emitters have great potential for achieving solution-processible, high-performance and stable blue OLEDs. [Display omitted] • D-π-A compounds based on benzo [4,5]thieno- S , S -dioxide-[3,2- b ]benzofuran (BTOBF) were synthesized and characterized. • CZ-Ph-BTOBF , DCZ-Ph-BTOBF and SAF-Ph-BTOBF show good thermal stability and pure blue emission characteristics. • Solvatochromic effect and HLCT excited state characteristics were observed. • Doped OLED devices were fabricated and characterized (EQE up to 6.85%). [ABSTRACT FROM AUTHOR]

Diesters of 1-pyrenecarboxylic acid with tri- and tetra - ethylene glycols were prepared and characterized for the first time and their photophysical and sensory properties were investigated. In aqueous solutions these compounds exhibited an intensive excimeric emission at 521 nm, which is attributed to the aggregation-induced fluorescence of the dimers, pre-associated in the ground state. In aqueous solutions an intensive "turn-off" fluorescence response towards common nitro-explosive components, such as 2,4-dinitrotoluene (2,4-DNT), 2,4,6-trinitrotoluene (TNT), as well as aliphatic nitro compounds, such as pentaerythritol tetranitrate (PETN), 1,3,5-trinitro-1,3,5-triazinane (RDX) and 2,3-dimethyl-2,3-dinitrobutane (DMDNB) was observed via the excimeric emission quenching. For the most representative chemosensor 4a the highest Stern-Volmer fluorescence quenching constant of 8.75 × 106 M−1 was observed in the presence of TNT. [Display omitted] • Bola-type pyrene end-capped fluorescent podands were prepared. • Aggregation-induced excimeric emission in aqueous THF was observed. • Great "turn-off" response to nitro-aromatic/aliphatic compounds was detected. • (0.97–8.75) × 10−6 M−1 quenching constants & 2–11 ppb LOD were determinated. [ABSTRACT FROM AUTHOR]

The hot exciton materials with high-lying reverse intersystem crossing provide great potential for the realization of efficient, low-cost and stable organic light-emitting diodes (OLEDs). However, it is highly desired but still challenging to achieve high-performance non-doped blue OLEDs with hot exciton luminogens. In this work, a new hybridized local and charge transfer (HLCT) luminogen 2-(4-(2-(4-(1,2,2-triphenylvinyl)phenyl)-1 H -phenanthro[9,10- d ]imidazole-1-yl)phenyl)phenanthro[9,10- d ]oxazole (abbreviated as TPE-PI-PO) with the incorporation of tetraphenylethylene is obtained for constructing the high-performance non-doped blue OLEDs. TPE-PI-PO possesses the multifunctional features of aggregation-induced emission (AIE), HLCT and mechanoluminescence with high photoluminescence quantum yield (58%) in the neat film. The non-doped OLEDs based on TPE-PI-PO exhibits sky-blue emission, high luminance of 13,020 cd m−2 and the maximum efficiencies of 11.62 cd A−1, 5.08% with the negligible efficiency roll-off as low as 1.6% at 1000 cd m−2. The electroluminescent performance is highly competitive with the best reported non-doped blue fluorescent OLEDs based on AIE luminogens. These results can shed light on a feasible design principle to develop high-quality HLCT-type luminogens for high-performance non-doped blue OLEDs. [Display omitted] • The sky-blue luminogen TPE-PI-PO is synthesized. • PE-PI-PO demonstrates the multifunctional property of HLCT, AIE and mechanoluminescence. • Non-doped OLEDs based on TPE-PI-PO achieve the EQE max of 5.08%. • Non-doped OLEDs demonstrate sky-blue emission with CIE of (0.26, 0.30). • Negligible efficiency roll-off of 1.6% at high luminance is displayed. [ABSTRACT FROM AUTHOR]

Excimer emission usually has a significant Stokes shift, making it an ideal candidate for constructing artificial light-harvesting systems (LHSs). However, the emission of excimers is altered by intermolecular interactions. Precise modulation of the spatial distance and interaction between luminescent units is the key to achieving enhanced emission of excimers. In the current study, electrostatic assembly of polyanionic PSS with cationic bolaamphiphile (PRB) containing pyrene was used to achieve close stacking of pyrene, resulting in significantly enhanced excimer emission. Furthermore, the morphology of the assemblies changed from nanodisks to nanospheres. In particular, the quantum yield of the PRB with PSS increased from 0.5% to 23.1%. In contrast, the amphiphilic molecule containing pyrene with a single hydrophilic head also showed enhanced fluorescence after being co-assembled with PSS. Nevertheless, the fluorescence quantum yield of excimers was much lower than that of the co-assemblies formed with PRB. The assembly formed by PSS and PRB acted as an energy donor. It underwent Förster resonance energy transfer with Nile red, achieving high energy conversion efficiency (Φ ET = 49.6%) and antenna effect (9.8) at a donor/acceptor molar ratio of 12.5:1. The electrostatic assembly induces enhanced excimers emission of pyrene derivatives to construct highly efficient artificial light-harvesting systems. [Display omitted] • The fluorescence emission of cationic amphiphilic pyrene derivatives can be modulated by polyelectrolytes. • The quantum yield of pyrene derivatives in aqueous solution was significantly enhanced by electrostatic assembly. • The co-assemblies were applied as donors to build light-harvesting systems with a high energy conversion efficiency. [ABSTRACT FROM AUTHOR]

Three organic ligands with 9-phenyl-9-phosphafluorene oxide (PhFlPO) group have been synthesized via successive nucleophilic aromatic substitution (S N Ar) reactions between dibenzothiophene dioxides and PhPH 2 -KOH under mild reaction conditions at room temperature. In this way, the novel PhFlPO-type organic ligands can be easily obtained without either highly sensitive Grignard or organolithium reagents of noble metal catalysts. Using these PhFlPO-type organic ligands, cyclometalated Ir(III) phosphorescent complexes with PhFlPO groups have been developed through well-accepted two-step strategy. To the best of our knowledge, these complexes represent the unprecedented examples of symmetric cyclometalated Ir(III) phosphorescent complexes bearing PhFlPO group. It has been found that electron-density on the coordinated carbon atom in the PhFlPO unit can exert a significant influence on the metal-to-ligand charge transfer transition (MLCT) processes and phosphorescent emission behavior of these cyclometalated Ir(III) phosphorescent complexes. In addition, the electroluminescent potential of these new cyclometalated Ir(III) phosphorescent complexes with PhFlPO groups has been characterized in solution-processed organic light-emitting diodes (OLEDs). They can show very impressively high external quantum efficiency (η ext), current efficiency (η L) and power efficiency (η P) of 20.0%, 71.7 cd A−1 and 56.1 lm W−1, respectively. These encouraging research results can furnish critical information for developing new PhFlPO-based Ir(III) phosphorescent emitters. Phosphorescent Ir(III) complexes with 9-Phenyl-9-phosphafluorene oxide organic ligands for highly efficient solution-processed OLEDs. [Display omitted] • Synthesis of ligands with 9-phenyl-9-phosphafluorene oxide group by successive nucleophilic aromatic substitution reactions. • Organic ligands with pyridyl group substituted on different position on the 9-phenyl-9-phosphafluorene oxide unit. • Symmetric Ir(III) phosphorescent complexes with 9-phenyl-9-phosphafluorene oxide group showing high EL efficiencies. [ABSTRACT FROM AUTHOR]

Donor-σ-acceptor molecules featuring exciplex emission have been extensively researched for developing thermally-activated delayed fluorescence; however, varying the length of alkyl σ-linker to explore the exciplex emission and to develop efficient exciplex emitters has not been fully conducted. Herein, we report donor-σ-acceptor exciplex emitters (1–3) developed with 9,9-dimethyl-10-phenyl-9,10-dihydroacridine donor, 2,4,6-triphenyl-1,3,5-triazine acceptor, and alkyl σ-linkers of different lengths (−CH 2 − for 1 , –CH 2 CH 2 − for 2 , and –CH 2 CH 2 CH 2 − for 3). The chemical structures of 1 – 3 have been verified by X -ray crystallography. Theoretical calculations reveal that intramolecular through-space charge transfer is the dominant charge-transfer mechanism within the molecules. In dilute solution and the films with low concentration of the dopant, intramolecular exciplexes are formed, whereas in the films with high concentration of the dopant, both intra- and inter-molecular exciplexes are formed. 1–3 all show aggregation-induced emission properties. In heavily doped or neat films, 1–3 show sky-blue emission with photoluminescent efficiency of up to 0.70 and high reverse intersystem crossing rates of up to 5.1 × 106 s−1. It is shown that varying the length of alkyl σ-linker regulates the thermally-activated delayed fluorescence of the exciplex formed in neat film. Vacuum-evaporated and solution-processed organic light-emitting diodes using 1–3 as the emitters show sky-blue and blue electroluminescence with peak external quantum efficiencies of up to 14.5% and 13.0%, respectively. The efficiency is among the highest for solution-processed blue organic light-emitting diodes based on small-molecule exciplex emitters reported so far. • Donor-σ-acceptor emitters were prepared with alkyl σ-linkers. • The length of the alkyl σ-linker was varied to tune the emission properties. • The emitters showed high k risc of up to 5.1 × 106 s−1 in films. • Solution-processed blue OLEDs using the emitters showed high EQEs of up to 13%. [ABSTRACT FROM AUTHOR]

A series of new dibenzoylmethanatoboron difluoride (DBMBF 2) and methoxy-substituted DBMBF 2 dyads linked via flexible diphenylsiloxane linkers of various length have been synthesized and characterized. The structure and optical properties of these compounds were studied by X-ray single-crystal measurements, electron absorption, and steady-state and time-resolved fluorescence spectroscopy. In the dyads under study, which are in an equilibrium between the open and folded conformations, the formation of intramolecular H-dimers in the ground state are observed. For the dyads in dilute solutions in various solvents, both monomer and excimer (through intramolecular excimer formation) emissions are observed at room temperature. The effect of solvent polarity and linker length on the formation of intramolecular excimers has been studied. The contribution of excimers into the total fluorescence spectrum decreases with increasing the solvent polarity, and the length of the siloxane linker. The studied dyads in hexane and cyclohexane solutions have CIE chromaticity coordinates very close to the white color point. The mechanofluorochromic properties of the synthesized dyads were studied. [Display omitted] • A series of new dibenzoylmethanatoboron difluoride dyads were synthesized. • The structure and optical properties of the dyads were studied. • The formation of intramolecular H-dimers in the ground state are observed. • For the dyads in dilute solutions both monomer and excimer emissions are observed. • The dyads have CIE chromaticity coordinates very close to the white color point. [ABSTRACT FROM AUTHOR]

Several functional and internal layers have been used to improve the performance of solution-processed Organic Light Emitting Diodes (OLED) devices. In the case of thermally activated delayed fluorescence (TADF) OLEDs, a large number of emitter materials have already been reported, but the design and development of potential host materials are overlooked. Efficient solution processable host materials for TADF OLEDs can reduce the complexity in the device architecture and production cost. In this work, we utilized a series of carbazole-based solution-processable host materials (ME4, ME5, ME9, ME10, and ME13) to fabricate the 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) based green TADF OLEDs. Among them, the ME9 composing device showed the best performance. The resultant device exhibited a maximum power efficacy of 40.0 lm/W, current efficacy of 44.7 cd/A, and external quantum efficiency of 14.1% with a maximum luminance of 16,220 cd/m2. The excellent performance may attribute to the low singlet-triplet energy gap (ΔE ST), high photoluminescence quantum yield (PLQY), high thermal stability, and unique porous morphology of the ME9. • Efficient host for solution processable TADF OLEDs. • Host with reduced ΔE ST and high PLQY (88.8%). • High performance attributed to the low ΔE ST and the unique porous morphology of the host material. • Both the host and the emitter can implement effective RISC. [ABSTRACT FROM AUTHOR]

Two new all- cis pyrene-substituted cyclic tetrasiloxanes (JR-01 and JR-02) are synthesized and studied as selective metal ion sensors. Both compounds exhibit solvent- and concentration-dependent excimer fluorescence emission at 482 nm. They also show highly selective fluorescence quenching by Au(III) ion with detection limits of 0.9 and 0.8 μM for JR-01 and JR-02 , respectively. Data from the Stern-Volmer's plots at various temperatures, zetasizers, NMR, and UV–Vis spectroscopy indicate a plausible mechanism involving the formation of a non-emissive Au(III) complex. An application of JR-01 as Au(III) sensor in real water samples reveals a good sensing efficiency which is comparable to the analysis result from ICP-QMS. In addition, when an excess amount of l -cysteine is added to the JR-01 /Au(III) mixture, the fluorescence signal is restored and the 1H NMR data suggests that JR-01 remains intact. As an extension of this study, we successfully demonstrate the detection of l -cysteine by fluorescence turn-on process using the JR-01 /Au(III) mixture with a detection limit of 14.0 μM. • Two new cyclic tetrasiloxanes are synthesized as selective Au(III) sensors. • The sensing mechanism involves the formation of a non-emissive complex. • The Au(III) complex can be used as a turn-on sensor for l -cysteine. [ABSTRACT FROM AUTHOR]

This article describes the synthesis and luminescent properties of two carbazole-functionalized 2-(benzo[ d ]thiazol-2-yl)phenol ligands (BTZ-Cz-OH and BTZ-DCz-OH) and their difluoroboron complexes (BTZ-Cz-BF and BTZ-DCz-BF) as the emitting materials. All of the emitting materials were characterized by NMR (1H and 13C) spectroscopy, high-resolution mass spectroscopy and elemental analysis, and they possess good thermal and electrochemical stabilities. The ligands exhibit green emission in solution and solid thin films due to the characteristics of excited-state intramolecular proton-transfer (ESIPT). Upon coordination to the difluoroboron complexes, a significant blue-shift and enhanced emission is observed due to the restricted conformation change. These materials are successfully used as the doped emitters in organic light-emitting diodes (OLEDs), and all the doped devices exhibit strong emission with low turn-on voltages (3.9–4.8 V), and the doped devices based on the difluoroboron complexes exhibit better EL performances than that of the ligands. Especially, the doped device of BTZ-Cz-BF with the dopant concentration of 10 wt% shows the best EL performances with a maximum luminescence of 3940 cd/m2, a maximum current efficiency of 8.26 cd/A and a maximum external quantum efficiency (EQE) of 3.34%. [Display omitted] • Two carbazole-functionalized 2-(benzo[ d ]thiazol-2-yl)phenol ligands and their difluoroboron complexes were synthesized and characterized. • The ligands exhibited the characteristics of excited-state intramolecular proton-transfer (ESIPT). • The solution-processed doped devices of the difluoroboron complexes showed L max of 3940 cd/m2, CE max of 8.26 cd/A and EQE max of 3.34%. [ABSTRACT FROM AUTHOR]

Four red homoleptic iridium (III) complexes (Ir1 – Ir4) with steric phenylphthalazine ligands have been synthesized. Single X-ray structural analysis shows that the steric hindrance groups can prevent molecular aggregation. All complexes exhibited red emission with peaks between 614 and 629 nm in CH 2 Cl 2 and photoluminescence quantum yields (QYs) of 44%–86% in doped films. They were concentration-insensitive, their QYs in neat powder and air atmosphere can reach a maximum of 15%. These complexes exhibited excellent thermal stability with T d higher than 416 °C. The OLEDs based on these complexes showed good performances at 10 wt% high doping concentration. Especially, the device based on Ir1 gave a peak current efficiency and external quantum efficiency (EQE) of 25.0 cd A−1 and 24.2% with mild efficiency roll-off, which is the most efficient OLED based on phthalazine iridium complexes. The maximum EQEs of non-doped devices are between 4.0% and 5.6%, which are considerably high, compared with the reported efficiency of iridium complexes based red-emitting non-doped devices. These studies show that increasing the density of the rigid steric groups of iridium complexes is very effective to achieve high efficiency and low concentration sensitive red phosphorescent devices. Complex Ir1 exhibited the highest PLQYs of 0.86, T d of 419 °C and peak EQE 24.2%. [Display omitted] • 1, Four homoleptic Ir complexes with enhanced steric hindrance were synthesized. • 2, All complexes exhibited excellent thermal stability with T d higher than 416 °C. • 3, These complexes are red emitting and have high color purity. • 4, All complexes are concentration-insensitive with high QYs in neat films. • 5, The best device exhibited an EQE max of 24.2% with mild efficiency roll-off. [ABSTRACT FROM AUTHOR]

We synthesized a diphenylamine modified pyrene derivative, 4,9-diisopropyl-N,N,N′,N′-tetrakis-(4-methyl-biphenyl-3-yl)-pyrene-1,6-diamine (DITBDAP), and successfully applied it to deep-blue organic light-emitting diodes (OLEDs). The DITBDAP-based top-emitting OLED was featured by a high maximum external quantum efficiency (EQE max) of 20.6%, an extremely low CIE y (Commission International de L'Eclairage coordinates) of 0.04, a narrow full-width at half maximum of 16 nm, and a long lifetime of 250 h. We chose 6,12-bis[6-trimethylphenyl)]amino5-trimethylphenyl)]amino] pyrene (Bmpac) as the comparison material due to its similar structure to DITBDAP. The DITBDAP-based bottom-emitting OLED showed a better performance compared to that of the Bmpac-based OLED, with the T 95 lifetime (time to 95% of the initial luminance of 3000 cd m−2) of 250 h, which was more than twice that of the Bmpac-based OLED. In addition, the efficiency roll-off was extremely low at high brightness, which were 1% at 1100 cd m−2 and 5% at 3200 cd m−2. The synthesized DITBDAP has realized highly efficient and long-lifetime deep-blue OLEDs with the EQE up to 20.6% and CIE y as low as 0.04. • A synthesized 4,9-diisopropyl-N,N,N′,N′-tetrakis-(4-methyl-biphenyl-3-yl)-pyrene-1,6-diamine (DITBDAP) is reported. • The performance and lifetime of the OLED using DITBDAP as the emitting layer is significantly enhanced. • The maximum external quantum efficiency is 20.6%, and the CIE y is only 0.04. • The full-width at half maximum is narrowed down to 16 nm, and a long T 95 lifetime of 250 h is achieved. [ABSTRACT FROM AUTHOR]

In recent years, AIE (aggregation-induced emission) fluorophores have attracted great interest owing to their advantages in wide areas and many AIE fluorophores have be designed by combing conventional fluorophores with AIEgens that exhibiting AIE attributes. However, only few efficient AIEgens were developed. Here, novel dihydrobenzoquinolines (h-DHBQs 4a − e and f-DHBQ 5a), a new kind of AIEgens with strong AIE, are reported. DHBQs were synthesized by a catalyst-free multi-component reaction (MCR) in good overall yield and their optical properties were investigated through steady-state and transient fluorescence spectra, single-crystal diffraction, calculated HOMOs and LUMOs. It was found that DHBQs have these characteristics: a) strong AIE, that is, their fluorescence quantum yields lower than 4.1% in solutions, but high to 90.5% in crystals; b) efficient through-bond and -space conjugated nonaromatic central heterocycle; c) radiative-process-favored but non-radiative-decay-prevented self-assemblies; d) emissive excimers; and e) easily tunable fluorescence color. This work affords a new kind of AIEgens with excellent optical properties in solids and a strategy to develop AIEgens by constructing nonaromatic heterocycle using simple MCRs. Novel through-bond and -space conjugated dihydrobenzo[h]/[f]quinolines (h-DHBQs 4a − e and f-DHBQ 5a) can be synthesized by a catalyst-free multicomponent reaction (MCR) in good overall yields. Their fluorescence quantum yields are lower than 4.1% in solutions, but high to 90.5% in crystals because their self-assemblies promote radiative transition but prevent nonradiative transition. Unusually, intermolecular compact π–π stacking causes no conventional emission-quenching. [Display omitted] • Novel dihydrobenzoquinolines could be synthesized by a multicomponent reaction. • They show strong AIE with fluorescence quantum yields as high as 90.5% in crystals. • They have efficient through-space conjugated nonaromatic central heterocycles. • Their self-assemblies favor radiative decay but prevent non-radiative decay. • Formed excimers are emissive. [ABSTRACT FROM AUTHOR]

Two red-emitting IrIII(C^N) 2 (P-donor ligand)Cl-type complexes bearing C^N ligands with carbazole functional group have been successfully prepared with different P-donor ligands of triphenylphosphine and triethylphosphine, respectively. The investigation of their phosphorescent behavior in the mixture of THF and water to reveal their aggregation induced phosphorescent emission (AIPE) ability, which is also indicated by their much higher phosphorescent quantum yield (Φ P) in doped film than those in the dilute solution. Mainly, their AIPE are induced by the blocked stretching motion of aromatic segments in C^N ligand and restrained the deformation of their coordinating skeletons. The AIPE complexes can possess AIE factor (α AIE) of ca. 7.4. In addition, the carbazole group can effectively promote hole transporting ability of the concerned AIPE emitters, which can benefit their electroluminescent ability. Hence, the IrIII(C^N) 2 (P-donor ligand)Cl-type complexes can show decent EL efficiencies in the solution-processed red-emitting organic Light-emitting diodes (OLEDs) with a maximum external quantum efficiency (η ext) of 8.5%, a maximum current efficiency (η L) of 22.0 cd A−1 and a maximum power efficiency (η P) of 15.9 lm W−1. Furthermore, as long-wavelength emitter, solution-processed white OLEDs (WOLEDs) have been constructed based on the red-emitting AIPE IrIII(C^N) 2 (P-donor ligand)Cl-type complexes, which can play critical role in achieving stable white electroluminescent spectra at high luminescence. The concerned WOLEDs can show attractive EL efficiencies of 6.6%, 23.7 cd A−1 and 16.0 lm W−1. All these results can provide valuable information for developing new AIPE materials with high EL ability. [Display omitted] • AIPE-active IrIII(C^N)(P-donor ligand)Cl-type complexes were prepared with different phosphine ligands. • Solution-processed red-emitting OLED showed a peak CE of 22.0 cd A−1. • Solution-processed white OLED showed a peak CE of 24.8 cd A−1 with CIE (0.31, 0.38). [ABSTRACT FROM AUTHOR]

This work identifies spiro[fluorene-9,9′-xanthene] (SFX) based luminophores could be promising single-molecule white emitters. Synthesized and tested are two SFX-based molecules, distinguishing by the absence (SFXDA) or the presence of chlorine substituents (2Cl-SFXDA) at the 3′,6′-positions of SFX core. The luminous proportion of monomer (higher energy band) and excimer (lower energy band) in the solid state was successfully lifted by the chlorine substituents in the molecular structure, based on which 2Cl-SFXDA presented an appropriate spectroscopic profile and emitted desirable white light. In their applications as single-molecule white emitter in light emitting devices, 2Cl-SFXDA -based devices exhibited high color purity with Commission Internationale de L'Éclairage coordinates of (0.31, 0.33). [Display omitted] • Spiro[fluorene-9,9′-xanthene]-based luminophore could be promising single-molecule white emitter was identified. • The luminous proportion of monomer and excimer in solid state was successfully regulated by atomic-scale substituents. • High color purity white light with CIE coordinates of (0.31, 0.33) was achieved for 2Cl-SFXDA -based LEDs. [ABSTRACT FROM AUTHOR]

α-Cyanostilbene derivatives are known as fluorescent photochromic molecules that could be used to realize emission colour change or on/off switching via photo-induced isomerization or cycloaddition. Comparing with isomerization, photocycloaddition is less studied due to its critical molecular position and alignment requirement for molecular packing. In this work, biphenyl-based cyanostilbenic compounds 1 – 3 were synthesized, which exhibit characteristic mechanofluorochromic (MFC) response behaviour. Under force stimuli, the luminescent colour has bathochromic shift from blue to green, together with the phase transition from crystal to amorphous state. Photochromic fluorescent response attributed to photo-induced [2 + 2] cycloaddition could take place instantly in amorphous state, rather than crystals. The MFC response can be successfully used to monitor the photoreaction process, giving rise to quantitative dimerized product. The single crystal structure of compound 2 revealed its photostable feature. The formation of excimers in ground amorphous state, together with the mechanical shearing, facilitates the occurrence of cycloaddition. Subsequently, the recovery process could be achieved thermally or under UV irradiation. [Display omitted] • Photo-[2+2] cycloaddition induced florescent responsetakes place in amorphous state, instead of crystalline state. • Machanochromic response with a transformation from crystals to amorphous solid turns on the photoactivity of compounds. • Machanochromic and photochromic response can be used to monitor the solid-state photoreaction process. [ABSTRACT FROM AUTHOR]

Highly efficient organic light emitting diodes based on thermally activated delayed fluorescence were fabricated using 9,9'-(sulfonylbis([ 1,1':3′,1″-terphenyl ]-5′,2′-diyl))bis(9 H -carbazole) as a host. The best device demonstrated high maximum external quantum efficiency of 23.3%, maximum current efficiency of 67.7 cd/A, maximum power efficiency of 60.9 lm/W with low efficiency roll-off. These characteristics were achieved due to the utilization of bipolar TADF host with tetraphenyl ornamenting. The molecular design strategy used allowed to obtain OLED host with the required combination of properties, i.e. triplet harvesting ability, perfect host→guest energy transfer, emission not affected by intermolecular interaction (no excimer/exciplex formation), high triplet level (2.98 eV), bipolar charge transporting properties, thermal stability up to sublimation temperature of 467 °C, amorphous forming properties with high glass transition temperature of 153 °C, good charge injecting properties (ionization potential of 5.9 eV and electron affinity of 2.8 eV). When the compound was used as TADF emitter, practically the same electroluminescent spectra peaked at 430 nm were obtained for deep-blue OLEDs with both non-doped and doped emitting layers. Such untypical electroluminescent behaviour of TADF OLEDs is attributed to the restricted by phenyl substituents changes of dihedral angels between donor and acceptor moieties and to reduced posibilities of the formation of the different conformers and aggregates in solid state. [Display omitted] • Design strategy of compounds with "frozen" TADF properties. • Doped and non-doped OLEDs with similar colors of their electroluminescence. • Derivative of tetraphenyl ornamented diphenyl sulfone and carbazole as OLED host. • TADF devices with high maximum external quantum efficiency of 23.3%. • Low roll-off efficiency resulting in EQE of 22.3% at 1000 cd/m2. [ABSTRACT FROM AUTHOR]

Herein disclosed the adjustment of the dual emission of keto and enol forms of excited-state intramolecular proton transfer (ESIPT) emitters via intramolecular charge transfer (ICT) effects. Introducing electron-donating triphenylamine (TPA) and electron-withdrawing triphenylboron (TPB) substituents into the para -position of the phenolic hydroxyl group or the side of the oxazole of 2-(2′-hydroxyphenyl)oxazole skeleton endows the resulting compounds (6a - 6d) with different photophysical properties. Owing to the ICT effect from electronic donor to acceptor, introducing TPA into the side of oxazole and TPB into the para -position of phenolic hydroxyl is conducive to an enol-form emission (6a). Exchanging the two substituents, namely introducing TPB into the side of oxazole and TPA into the para -position of phenolic hydroxyl, would be beneficial to a keto-form emission (6b). Synchronously introducing two identical substituents, whether TPA or TPB, into two sides of 2-(2′-hydroxyphenyl)oxazole skeleton (6c and 6d) would lead to the dual emission of keto and enol forms due to the excited-state equilibrium of ESIPT reactions, which are further verified by DFT calculation. The organic light-emitting diode (OLED) devices with 6a and 6c as emitters were fabricated, both of which exhibit hybridized local and charge transfer (HLCT) excited-state characters with high external quantum efficiencies (EQEs) of 4.9% and 5.6%, respectively. • The adjustment of keto/enol emission of ESIPT emitters was systematically investigated for the first time. • ICT effect was deduced to be the main driving force to lead to the different luminescence properties of these ESIPT emitters. • The excited-state equilibrium of ESIPT reactions is verified by DFT calculation. • OLEDs based on ESIPT emitters exhibit high external quantum efficiencies. • The HLCT characters of ESIPT emitters were confirmed by experimental data and theoretical calculations. [ABSTRACT FROM AUTHOR]

Deep-red (DR) emitting materials with narrow band gap have important applications in optoelectronic field. However, limited by energy gap rules, the development of DR emitting materials with high luminous efficiency face great challenges. Herein, we present a new Quinoxaline-based compound 6,7-bis(4-(diphenylamino)phenyl)quinoxaline-2,3-dicarbonitrile ( o -QxDC-DTPA) with D-A-D structure for deep-red organic light emitting diodes. Such a material features distinctive DR emitting property with strong charge transfer character. Highly efficient devices were achieved based on o -QxDC-DTPA with different doped concentrations. The doped device exhibited excellent electroluminescence efficiency, with a maximum EQE of 5.21% and DR emission with the emission peak at 680 nm. [Display omitted] • Quinoxaline-2,3-dicarbonitrile (QxDC) as a new acceptor is attached to triphenylamine for a highly efficient deep-red material ( o -QxDC-DTPA). • Experimental and theoretical results demonstrate the strong CT characteristic of o -QxDC-DTPA molecule. • The OLED based on o -QxDC-DTPA with strong CT state shows high EQE of 5.2% with the emission peak at 680 nm. [ABSTRACT FROM AUTHOR]

Non-linear optical effects (NLO) such as multi-photon absorption, second harmonic generation (SHG) etc. have a wide range of applications. Nevertheless, the performance of many NLO-active organic dyes is limited by their thermal stability and photobleaching. These problems can be overcome by integrating the dyes into coordination polymers or metal-organic frameworks. Here, we present a structural and photophysical study of dipropyl-9-(4-nitrophenyl)-carbazole-3,6-dicarboxylate, a new "push-pull" organic dye molecule designed as a chromophore linker for NLO-active coordination polymers. Structure determination of a single-crystal showed that it crystallizes in a monoclinic crystal system P 2 1 / c. The solvated chromophore exhibits two aromatic absorption bands at 250 nm and 275 nm as well as broad long wavelength band at 350 nm, which we assign to an intramolecular charge transfer state. Photoluminescence measurements in solvents of different polarities revealed two main effects: In nonpolar solvents, the spectrum shows an emission band at 360 nm, whereas in solvents with a higher polarity, the emission maximum broadens and redshifts. Solid-state emission measurement of sample powder exhibits an emission band at 520 nm which is redshifted compared to the measurements in solution, due to excimer formation in the solid-state. The optical as well as solvation-related properties of the investigated pigment render it to be a versatile ligand in coordination polymers. Image 1 • Structural and photophysical study of a new carbazole based "push-pull" organic dye. • In solution molecule exhibits an solvatochromic intramolecular charge transfer emission. • In solid-state parallel packing of chromophore leads to excimer emission. [ABSTRACT FROM AUTHOR]

A new (4-(3,5-dimethylphenyl)-2-(m-tolyl)pyridine)-based iridium complex was synthesized for highly efficient orange phosphorescent organic light-emitting diodes (PhOLEDs). The effect of introduction of a methyl substituent into the 4-position of the phenyl ring in a phenylpyridine chelating ligand was studied. The PhOLEDs based on this newly-synthesized iridium complex exhibited maximum external quantum and current efficiencies of 20.33% and 61.16 cd/A, respectively. These respective values maintained over 15% and 48 cd/A even at a very high luminance of 15000 cd/m2 with Commission Internationale de l'Eclairage coordinates of (0.49, 0.51). In this work, a new (4-(3,5-dimethylphenyl)-2-(m-tolyl)pyridine)-based iridium complex (Ir(dmpmpy) 2 (acac)) was synthesized for highly efficient orange phosphorescent organic light-emitting diodes (PhOLEDs). The effect of introduction of a methyl substituent into the 4-position of the phenyl ring in a phenylpyridine chelating ligand was studied. The PhOLEDs based on this newly-synthesized iridium complex exhibited maximum external quantum and current efficiencies of 20.33% and 61.16 cd/A, respectively. These respective values maintained over 15% and 48 cd/A even at a very high luminance of 15000 cd/m2 with Commission Internationale de l'Eclairage color coordinates of (0.49, 0.51). Image 1 • A new orange emission iridium complex was synthesized. • Methyl substituent introduced at phenyl pyridine chelating ligand. • The maximum EQE of 20.33% and CE of 61.16 cd/A are achieved. • The EQE and CE maintained over 15% and 48 cd/A at 15,000 cd/m2. [ABSTRACT FROM AUTHOR]

The ternary hybrid thin films of poly [9,9′-di- n -octylfluorenyl-2,7-diyl] (PFO)/poly [2methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/2-butyl-6- (butylamino) benzo [de] isoquinoline-1,3-dione (F7GA) were successfully prepared with various ratios of F7GA. Dual Förster resonance energy transfer (FRET) from PFO to both F7GA and MEH-PPV was confirmed in the ternary thin films. The distance between PFO and F7GA molecules was smaller than the distance between PFO and MEH-PPV. Besides, white light emission was achieved with cascade energy transfer in this ternary blend system. The lifetime decay components of the acceptor emission were attributed to the presence of an exciplex between the molecules in the acceptor excited state and the donor ground state. In addition to the dual FRET, carrier trapping took place in the device, successfully realizing white organic light-emitting diodes (WOLEDs). The maximum luminance of 2295 cd/m2 and a current density of 12.98 mA/cm2 at CIE coordinates of (0.31, 0.24) was achieved with the device at 1.0 wt% F7GA. Image 1 • Dual FRET efficiency was increased from 88.7% to 99.4% with addition of F7GA. • The R o values were in the range 84.6 ــ 37.0 Å, confirming the dominant FRET. • The long lifetime decays at 495 nm and 570 nm, suggesting the exciplex formation. • Charge trapping effect in conjunction with dual FRET can be occurred in the WOLEDs. • The optimal WOLED was for emissive layer with 1.0 wt% F7GA in the ternary blend. [ABSTRACT FROM AUTHOR]

2-(12H-benzofuro[3,2- a ]carbazol-12-yl)dibenzo[b,d]thiophene 5,5-dioxide (DBT-INFUR) is a bipolar host material for yellow and red phosphorescent OLEDs. DBT-INFUR was designed and synthesized between dibenzothiphene acceptor and benzofuro carbazole donor with a yield of 60%. We constructed two different devices, namely a yellow and a red phosphorescent OLEDs, and we compared the device properties with reference 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP). DBT-INFUR based yellow phosphorescent OLED device exhibited maximum current and external quantum efficiencies of 41.07 cd/A and 16.5%, respectively and which is better than that of reference CBP based similar device (27.66 cd A, 10.15%). DBT-INFUR based red phosphorescent OLED (12.44%) revealed higher efficiencies when compared to the reference (7.64%) device. The bipolar DBT-INFUR showed excellent host properties with yellow and red phosphorescent devices. • Maximum current efficiency achieved 41.07 cd/A for yellow PhOLED. • Excellent external quantum efficiency of 16.5% obtained for yellow PhOLEDs. • DBT-INFUR showed better device performance than reference material. • Dibenzothiophene dioxide and benzofuro carbazole based materials are suitable as host for phosphorescent OLEDs. [ABSTRACT FROM AUTHOR]

In this work, we designed a dual-fluorophore-based water sensor 5-(dimethylamino)- N'-(pyren-1-ylmethylene)naphthalene-1-sulfonohydrazide (PDH) by combining pyrene, which exhibits monomer/excimer switching emission, and dansyl, which shows typical intramolecular charge transfer (ICT) activity. The effects of solvents on PDH and two control compounds were studied. Results showed that PDH exhibited tunable fluorescence properties, and the two fluorescent units of PDH could behave independently and synergistically. Generally, the fluorescent emission of PDH displayed two distinct modes in various solvents. On the one hand, only pyrene emission was observed in N, N-dimethylformamide (DMF), acetonitrile (AN), ethanol (EtOH), dimethyl sulfoxide (DMSO), methanol (MeOH), acetone, and tetrahydrofuran (THF) because these solvents affected the push–pull interactions between dimethyamino moiety and naphthalenesulfonyl and the aggregation behavior. On the other hand, efficient Förster resonance energy transfer (FRET) from the pyrene unit to the dansyl moiety was observed in dichloromethane (CH 2 Cl 2), chloroform (CHCl 3), ethyl acetate (EA), toluene, and water (H 2 O). The fluorescence spectra displayed strong dansyl emission and weak pyrene monomer emission due to the synergy of ICT and FRET. By taking advantage of the monomer/excimer switching, ICT, and FRET activities, the fluorescence tunability of PDH was applied for the differentiation of solvents and discriminative detection of H 2 O content in three organic solvents, including acetone, DMF, and DMSO. • A dual-fluorophore-based fluorescent sensor was developed by combining pyrene and dansyl groups. • The differentiation of solvents was realized on the basis of the blue and green fluorescence emissions. • The sensor was successfully applied for the discriminative detection of water content in organic solvents. [ABSTRACT FROM AUTHOR]

Herein, the temperature-dependent fluorescence properties of a hexacatenar liquid crystalline (LC) molecule composed of naphthalenyl and 1,2,3-triazolyl linkers are reported. This molecule exhibited a bluish emission in its crystalline and LC phases under UV-irradiation. According to the obtained photoluminescence (PL) and lifetime data, the emission originated from excimer formation of the naphthalenyl units. Morphological analyses indicated the face-to-face stacking of the naphthalenyl units in the orthorhombic crystalline (Cry ortho) and helical columnar LC (Col hel) structures. This packing mode was used to rationalize the excimer emission from the PL data. As temperature increased to 100 °C, the PL intensity gradually decreased. Interestingly, it dropped abruptly at 100 °C in the LC temperature range. Dielectric relaxation spectroscopic analysis indicated that molecular reorientation allowing full rotational motion was initially activated at 100 °C. The sudden variation in the rotational rigidity was associated with triazolyl hydrogen-bonding, which affected the emission intensity. Image 1 • A bluish excimer emission persists even at the transition from crystal to LC phase. • Both helical columnar crystalline and LC structures consist of face-to-face stacking of adjacent aromatic cores. • A sudden reduction in the emission intensity occurs in the middle of LC phase. • The molecular dynamics from DRS study supports the unusual emission reduction. • Degree of hydrogen bonding with temperature is the key factor to determine the molecular dynamics. [ABSTRACT FROM AUTHOR]

A low molecular mass organic gelator (LMOG) T16 was obtained by introducing a long alkyl chain into an excimer precursor α–CN–TPA. Immobile organogels of T16 exhibiting both thermochromic and mechanochromic fluorescence switching between blue and green could be formed. Far more than expected, the long alkyl chain endows T16 with unique two channels of twisted intramolecular charge transfer (TICT) emission in solution and highly luminescent properties in both a gel and solid state (crystal). The fluorescence distribution ratio of the two channels is dependent on irradiation wavelength and solvent polarity, leading to distinct effects of aggregation induced enhanced emission (AIEE) and gelation induced enhanced emission (GIEE), respectively. The fluorescent quantum efficiency of T16 is increased more than 380 times in xerogel and almost 500 times in the crystal compared with that of α–CN–TPA crystal, though both molecules have the same conjugated unit. The radiant transition is found to be transformed from a forbidden state in α–CN–TPA to the allowed state in T16, owing to the incorporation of a long alkyl chain which influences the self-assembly structure and intermolecular interactions. Antiparallel molecular H-stacking and multi-layered self-assembly are constructed in T16 under the driving force of π−π, electrostatic and long alkyl-alkyl chain interactions. These findings offer a simple and interesting platform for manipulating the fluorescence radiation characteristics. Image 1 • A low molecular mass organic gelator with switchable luminescence was synthesized. • The gelator exhibits two channels of twisted intramolecular charge transfer emission. • The radiant transition is found to be transformed from a forbidden state to the allowed one. • Introducing a long alkyl chain into an excimer precursor is a strategy to develop highly luminescent organogelators. [ABSTRACT FROM AUTHOR]

A new 9-phenylfluorene functionalized 2,6-bis(N -carbazolyl)-pyridine compound 2,6-bis(3-(9-phenyl-fluoren- 9-yl)-carbazol-9-yl)pyridine (2 , 6-PFCzPy) with large steric hindrance and high triplet energy level has been successfully prepared by introducing 3-(9-phenyl-fluoren-9-yl)-carbazole unit into the 2,6-position of pyridine group via Ullmann reaction. Cyclic voltammetry (CV) was used to study the electrochemical properties of the compound and obtain HOMO (−5.85 eV), LUMO (−2.09 eV), and energy gap (E g , 3.57 eV). The 2,6-CzPy-based compound was employed as host to fabricate blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) for the first time with the maximum EQEs of 6.2% at the doping concentration as high as 30%. The electroluminescent (EL) spectra show almost no changes along with the driving voltage ranging from 5.1 to 15.1 V at high doping concentration, which indicates the 2,6-CzPy-based three dimensional bulky compound could successfully suppress the excimer emission of the guest in high doping ratio. The first 2,6-bis(N -carbazolyl)-pyridine-based compound with large steric hindrance was employed as host for blue TADF OLEDs with stable EL spectrum under different driving voltages at doping concentration as high as 30%. Image 1 • The first 2,6-bis(N -carbazolyl)-pyridine-based compound with large steric hindrance was used as host for blue TADF OLEDs. • Stable blue EL spectra were achieved under different driving voltages at high doping concentration of 30%. • The enhanced thermal and morphological stability was achieved with high triplet energy level (T 1 , 2.83 eV) and controllable electrochemical properties. [ABSTRACT FROM AUTHOR]

In the current study we demonstrate an application of four previously synthesized 1,7-diphenyl-substituted BODIPY species for inverted photovoltaic cells and for organic light-emitting devices (OLEDs). Depending on the type of substituents or annulation of the pyridone rings these dyes exhibit spectral properties in the full visible region up to the near-infrared wavelengths. All the studied compounds show very strong visible absorption that can be ascribed to the low lying LUMO levels making them electronically suitable as acceptors for many donor materials. The best fabricated inverted photovoltaic device based on the BODYPI-core derivatives demonstrates a power conversion efficiency equal to 1.36% which is close to previously published reports for related species. Two kinds of deep red OLEDs (doped and undoped) with narrow electroluminescence spectra (full width at half maximum up to 45 nm) have been fabricated. Maximum brightness of 3900 cd m−2 and an external quantum efficiency by 2.3% were achieved for the best OLED structure. Image 1 • Several BODIPY-core derivatives have been used for the fabrication of OLEDs and inverted OPV cells. • The designed OLEDs are characterized by the deep-red emission and narrow spectra. • Inverted OPV cells demonstrates the clear dependence of performance on the energies of HOMO/LUMO levels. • Cyclic voltammetry measurements show the dependence of HOMO/LUMO energies on the chemical structure of BODIPY derivatives. • Quantum-chemical calculations support the electrochemical measurements and electronic spectra. [ABSTRACT FROM AUTHOR]

Six 2,5-diamino-3,6-dicyanopyrazine dyes with medium to long length alkyl chains on their amino groups were newly synthesised and their fundamental properties investigated, including their derivatives, focusing on liquefaction at room temperature. The butyl, pentyl, hexyl, heptyl, octyl, and dodecyl substitutions realised liquefaction of the dye chromophore. These liquid dyes exhibited relatively good fluorescent properties in the liquid state. The dodecyl derivative showed the largest fluorescence efficiency of 0.59 in the liquid state among the derivatives and was used in an organic light-emitting device. The efficient yellow EL emission peaked at 593 nm with a 10 V turn-on voltage of the device and a maximum brightness of 336 cd/m2 at 14 V. Image 1 • A series of alkylated pyrazine dyes focusing on the liquefaction were investigated. • The alkyl group in the dye system drastically affected the melting point of the dyes. • The liquid dyes exhibited relatively good fluorescent properties in a liquid state. • One of the liquid dyes was applied to an organic light-emitting device. • The efficient yellow EL emission was obtained in the prepared OLED. [ABSTRACT FROM AUTHOR]

Fluorescent ratiometric probes based on monomer/excimer of pyrene group are often used to detect cations. However, only a few pyrene-containing ratiometric pH probes have been reported so far, and almost all of them produce intramolecular pyrene excimer. In this work, three new ratiometric fluorescent pH probes based on intermolecular pyrene excimer, pyrene-1-carboxamide (1), N-(2-hydroxyethyl)pyrene -1-carboxamide (2) and N,N-bis(2-hydroxyethyl) pyrene-1-carboxamide (3), were synthesized. These probes, 1 , 2 , and 3 , have p K a value of 1.93, 1.85 and 2.07, respectively, and can fluorescently determine the pH value of the extremely acidic aqueous solution with a detection range of about 1.0–2.5. When the pH value was decreased from 2.5 to 1.0, these probes showed a ratiometric fluorescent response signal due to the conversion of monomer/excimer of pyrene group. Therefore, intermolecular excimer of the pyrene group from these probes can be produced in extremely acidic environment. Further tests show that these probes have potential as excellent pH fluorescent probes, with high sensitivity, fast response time, good photostability, strong anti-ion interference ability and high repeatability, etc. The applicability of these probes was demonstrated with environment water samples. In addition, fluorescent pH test paper was successfully developed, which can monitor pH values in the solution through pH-related change of fluorescent color of the probes. The ratiometric fluorescent probes based on intermolecular pyrene excimer, 1 , 2 and 3 , can detect pH value of the extremely acidic water environment (distilled water, tap water and Zhujiang River water) with high sensitivity, fast response time, good photostability, strong anti-ion interference ability and good repeatability. Image 1 • Probes 1-3 can ratiometric fluorescent measurepH valuein the range of about 1.0–2.5. • Probes 1 - 3 showhigh sensitivity, fast response timeandgood photostability. • Probes 1 - 3 showstrong anti-ion interference ability andgood repeatability. • Probes 1-3 can be used in thedetectionpH value ofthe environmental water samples. • Probes 1-3 can be used in the productionofpH test paper. [ABSTRACT FROM AUTHOR]