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Two novel molecular scaffolds, dibenzo[f,h]furo[2,3-b]quinoxaline (diBFQ) and its derivative, 3,6-bis(4-isopropylphenyls)-11-phenyldibenzo[f,h]furo[2,3-b]quinoxaline (dP-diBFQ), and furo[2',3':5,6]pyrazino[2,3-f][1,10]phenanthroline (FPPhen), were designed and syn-thesized for highly efficient pure and deep blue emission. The unsubstituted molecule scaffold diBFQ and FPPhen exhibit 424~445 nm emission with ~70% PLQY, and disubstituted derivative of diBFQ, dP-diBFQ, shows 79.1% PLQY. Our experimental and theoretical investigations re-vealed the additional N atoms in FPPhen facilitate electron distribution of HOMO orbital localizing on smaller π-conjugate fragment as com-pared with diBFQ, which resulted in emission peak blue-shifting from 445 nm of diBFQ to 424 nm of FPPhen. Furthermore, introducing the steric substituent isopropylphenyl into diBFQ scaffold would help to suppress aggregate of dP-diBFQ molecules and improve fluorescence efficiency. The OLEDs using dP-diBFQ as dopants shows pure blue emission with a CIE coordinates (0.154, 0.102) and an EQE of 2.28%. In-creasing dopant concentration, the EQE and current efficiency could be improved to 2.63 % and 4.7 cd/A, but aggregate emission with a peak of 472~476 nm was clearly observed due to molecular aggregate. Our studies clearly suggested that diBFQ and FPPhen scaffolds are promising fluorescence core for deep and pure-blue emissions.

Two-dimensional (2D) organic–inorganic hybrid materials have attracted widespread attention for photodetection. Moreover, such materials with broadband photoluminescence and strong photocurrent response are still rare. Here, we report two new semiconducting 2D organic–inorganic hybrid materials, namely {PbII2I6[PbII(TETA)]}n (1Pb) and {PbII3I8[PbII(TETA)]}n (2Pb), where TETA = triethylenetetramine, with broadband yellow-green emission. Both compounds are soluble in DMF and yield high surface coverage films through spin coating. Strikingly, the photocurrent responses of such thin films show ca. 600 and 700 nA cm−2 difference between Ilight and Idark for 1Pb and 2Pb, respectively. To the best of our knowledge, 1Pb and 2Pb showed among the highest current obtained in 2D lead iodide hybrid materials under a low voltage (0.7 V). Moreover, 1Pb and 2Pb are stable under heat, moisture and light, which may provide realistic applications for light detection.

We studied the inhibitory effects of allelochemicals extracted from celery (Apium graveolens L.) rotten roots and rhizosphere soil on Fusarium oxysporum f. sp. cucumerinum (FOC). The allelochemicals were extracted and separated by column chromatography from the acetone extracts of celery rotten roots and rhizosphere soil. After extraction each fraction was mixed with potato dextrose agar (PDA) culture medium and then inoculated with FOC. The best fraction was screened by measuring the colony diameter and its effects on FOC was determined by evaluating the activities of antioxidant enzymes. The allelochemicals of best fractions were detected using GC-MS. The best fractions obtained after second run in column chromatography were labeled as RRA32, RRA38, RRA101, RRA102 and RRSA55, RRSA56, RRSA105, RRSA106 and they had allelopathic potential of 29.68 %, 31.97 %, 40.38 %, 41.55 % and 29.51 %, 29.47 %, 29.30 % and 32.85 % respectively. The antioxidants enzymes (peroxidase, catalase and superoxide dismutase) activities were significantly lower in treated FOC than control. Using the 8-best fractions, the GC-MS analysis yielded, total 47 compounds viz., 7 organic acids, 17 esters, 1 phenol, 1 alcohol, 1 aldehyde, 5 nitrogen-containing compounds and 2 carbides.

Inspired by the intriguing optoelectronic characteristics of the 2-phenylpyridine-type (ppy-type) four-coordinate organoboron skeleton, we envisage a molecular design strategy by manipulating the MLCT transition character to develop high-performance long-wavelength Ir-based phosphors with a ppy-type four-coordinate organoboron skeleton for organic light-emitting diodes (OLEDs). Three ppy-type cyclometalated Ir(III) complexes are successfully prepared. IrOBN and IrPBN exhibit the expected long-wavelength phosphorescent emission at 620 and 604 nm, respectively, due to the electron-accepting ability of the pyridine coordinated with the boron atom (pyd(B)) in extending the π-conjugated length for the LUMO, thus leading to stabilization of the LUMO. Interestingly, IrMBN shows a green phosphorescence at 514 nm. The more electron-deficient pyd(B) in IrMBN leads to a reorganized and localized LUMO distribution pattern mainly on pyd(B) rather than the pyridine coordinated with the Ir atom (pyd(Ir)), shortening the π-conjugation length for the LUMO, hence resulting in an elevated LUMO. Benefiting from the high rigidity of the ppy-type four-coordinate organoboron skeleton, these three ppy-type cyclometalated Ir(III) complexes show high PLQY (ca. 0.6–1). Beneficially, we can achieve impressive electroluminescence (EL) performance based on IrPBN with the highest efficiencies of a maximum external quantum efficiency (ηext) of 26.0%, a maximum current efficiency (ηL) of 42.0 cd A−1, and a maximum power efficiency (ηP) of 38.5 lm W−1, respectively. All these excellent results convincingly demonstrate the effectiveness of our molecular design strategy and the great potential of the ppy-type four-coordinate organoboron skeleton in developing high-performance Ir-based phosphors.

Lead-based semiconducting organic–inorganic halides such as CH3NH3PbI3 are promising materials for optoelectronic applications. However, the toxicity of lead and the instability of these materials could raise environmental issues if they are applied on a large scale. Herein, two new 2D lead-free bimetallic iodide-based hybrid compounds are presented, namely (C12H30N4)Cs3BiI8 (CsBiI-1) and (C14H35N4)CsBiI7 (CsBiI-2), using different amines: C6H14N2 = cyclohexane-1,4-diamine (CDA) and C7H16N2 = 2-piperidinoethylamine (PDA). These two compounds show optical band gaps of 2.18 eV and 2.39 eV for CsBiI-1 and CsBiI-2, respectively. Both materials yield high surface coverage films from spin-coating. Moreover, CsBiI-1 and CsBiI-2 are stable under moisture and present photocurrent responses. Thus, these materials have the potential for use in light detection.

The halide perovskite Ruddlesden-Popper (RP) phases are a homologous layered subclass of solution-processable semiconductors that have aroused great attention, especially for developing long-term solar photovoltaics. They are defined as (A′)2(A)n-1PbnX3n+1 (A′ = spacer cation, A = cage cation, and X = halide anion). The orientation control of low-temperature self-assembled thin films is a fundamental issue associated with the ability to control the charge carrier transport perpendicular to the substrate. Here we report new chemical derivatives designed from a molecular perspective using a novel spacer cation 3-phenyl-2-propenammonium (PPA) with conjugated backbone as a low-temperature strategy to assemble more efficient solar cells. First, we solved and refined the crystal structures of single crystals with the general formula (PPA)2(FA0.5MA0.5)n-1PbnI3n+1 (n = 2 and 3, space group C2) using X-ray diffraction and then used the mixed halide (PPA)2(Cs0.05(FA0.88MA0.12)0.95)n-1Pbn(I0.88Br0.12)3n+1 analogues to achieve more efficient devices. While forming the RP phases, multiple hydrogen bonds between PPA and inorganic octahedra reinforce the layered structure. For films we observe that as the targeted layer thickness index increases from n = 2 to n = 4, a less horizontal preferred orientation of the inorganic layers is progressively realized along with an increased presence of high-n or 3D phases, with an improved flow of free charge carriers and vertical to substrate conductivity. Accordingly, we achieve an efficiency of 14.76% for planar p-i-n solar cells using PPA-RP perovskites, which retain 93.8 ± 0.25% efficiency with encapsulation after 600 h at 85 °C and 85% humidity (ISOS-D-3).

Low-toxicity tin-based perovskites have exhibited huge potential for photovoltaics applications. However, the facile oxidation of Sn2+ to Sn4+ induces ubiquitous Sn vacancies and p-type doping in p...

To best catch human eyes in next-generation displays, the updated recommendation 2020 (Rec. 2020) standard has called for ultrapure green emitters to be qualified with a narrow emission of 525-535 nm with a full width at half-maximum (fwhm) below 25 nm. However, it is still challenging to find an emitter which can simultaneously cover these two criteria. Instead of traditional II-VI group semiconductor quantum dots, perovskite nanocrystals (NCs) can render versatile emitting tunability to allow them access to the Rec. 2020 standard. Herein, to realize the critical window of Rec. 2020, we have proposed a scalable, room temperature synthesis route of formamidinium lead bromide (FAPbBr3) NCs using a sole ligand of sulfobetaine-18 (SBE-18). The as-synthesized FAPbBr3 NCs exhibit an ideal emission at 534 nm with an ultranarrow fwhm of 20.5 nm and a high photoluminescence quantum yield of 90.6%, overwhelming the FAPbBr3 nanoplates capped with oleic acid/oleylamine (OA/OAM). Introducing these high quality NCs into backlight displays, an ultrapure green backlight which covers ≈85.7% of the Rec. 2020 standard in the CIE 1931 color space is achieved, signifying the "greenest" backlight till now. Thus, we can foresee perovskite NCs as the most potential candidates for next-generation displays.

A series of 2-phenylpyridine (ppy)-type cyclometalating ligands containing rigid 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (OBA) units have been developed. Together with different ppy-type cyclometalating ligands with a phenylsulfonyl group (–SO2Ph) substituted at different positions, new unsymmetric heteroleptic cyclometalated Ir(III) complexes have been successfully synthesized. Their photophysical, electrochemical and electroluminescence (EL) behaviors have been fully characterized. In addition, both time-dependent functional theory (TD-DFT) and natural transition orbital (NTO) theoretical results have been obtained to gain insight into the optoelectronic behaviors of these unsymmetric Ir(III) complexes with OBA units. The NTO results indicate that the features of the lowest triplet excited states (T1) can be delicately tuned by combination between the OBA-based cyclometalating ligand and another ppy-type ligand with the –SO2Ph group. Importantly, these unsymmetric Ir(III) complexes can exhibit very high phosphorescence quantum yield (Φp) higher than 0.90 due to the highly rigid OBA unit which can effectively restrain non-radiative processes. In addition, an electron injection/transporting (EI/ET) ability can be conferred to these unsymmetric heteroleptic cyclometalated Ir(III) complexes by both OBA and –SO2Ph moieties. Taking advantage of these merits, organic light-emitting diodes (OLEDs) based on these unsymmetric heteroleptic cyclometalated Ir(III) complexes can show a high maximum external quantum efficiency (ηext) of 12.8%, a current efficiency (ηL) of 51.1 cd A−1, and a power efficiency (ηP) of 40.5 lm W−1 for a yellowish-green device, while EL efficiencies for red devices are 6.8%, 13.9 cd A−1, and 12.8 lm W−1, respectively. All these results indicate the good potential of the rigid OBA unit in developing functional phosphorescent emitters.

The energy level alignment and carrier mobility of the charge transport layer are of crucial importance for electron extraction and transport in planar heterojunction perovskite solar cells (PSCs). In this work, a carbon nitride modified SnO2 nanocomposite, SnO2/graphitic carbon nitride (g-C3N4) quantum dots, was designed as the functional electron transport layer (ETL) to precisely regulate the interfacial charge dynamics for high-performance PSCs. It is demonstrated that the g-C3N4 could recast the electronic density distribution around the neighboring SnO2 crystal unit, thus effectively eliminating the oxygen-vacancy-reduced trap centers and promoting the interface and bulk electron transport. Consequently, this carbon nitride modified SnO2 nanocomposite exhibits appropriate electrical properties including suitable energy level alignment and high conductivity. Employing the typical hybrid SnO2-based ETL, a maximum power conversion efficiency (PCE) of 22.13% (Voc = 1.176 V, Jsc = 24.03 mA cm−2, FF = 0.783) can be achieved for planar heterojunction PSCs, with negligible hysteresis and long-term stability (only 10% PCE decay after 1500 h at a relative humidity of 60%). Our work offers a hybrid ETL design strategy to improve the efficiency and stability of PSCs.

The environmental toxicity of lead may eventually hamper the wide applications of hybrid perovskite material-based solar cells despite their excellent power conversion efficiency. Here, we have used silver(I) and bismuth(III) to replace lead(II) and obtain two two-dimensional (2D) iodide-based double perovskites, (AMP)4[BiAgI8]2·H2O (1) and (APP)4[BiAgI8]·H2O (2), where AMP = 4-aminomethylpiperidine and APP = 4-aminopiperidine. Compared to our previously reported 1,4-cyclohexanediamine-based compound (C6H16N2)2[BiAgI8]·H2O with an indirect band gap, these two new 2D Ag–Bi double perovskites show direct band gaps (∼2.00 eV) due to the less distorted [AgI6] coordination geometry. Moreover, the photo-current response experiments showed a difference of more than 50 nA between light and dark conditions for both the compounds, indicating the potential application for light harvesting. 1 and 2 were also stable under heat and moisture. They showed high proton conductivity (∼10−4 S cm−1) at 95 °C and 90% RH. Thus, this work provides a new route for designing stable lead-free bimetallic iodide double perovskites with direct band gaps.

Recently, perovskite light-emitting diodes (PeLEDs) have drew widespread attention due to their high efficiencies. However, because of the sensitivity to moisture and oxygen, perovskite luminescent layers are usually prepared in high-purity nitrogen environment, which increases the cost and process complexity of device preparation and seriously hindrances its commercialization of PeLED in lighting and display application. Herein, dual-phase all-inorganic composite CsPbBr3-Cs4PbBr6 films are fabricated from CsBr-rich perovskite solutions by a simple one-step spin-coating method in the air with high humidity. Compared with the pure CsPbBr3 film, the composite CsPbBr3-Cs4PbBr6 film has much stronger photoluminescence emission and longer fluorescence lifetime, accompanied by increased photoluminescence quantum yield (33%). As a result, we obtained green PeLED devices without hole transport layer exhibiting a maximum brightness of 72,082 cd/m2 and a maximum external quantum efficiency of about 2.45%, respectively. More importantly, the champion device shows excellent stability with operational half-lifetime exceeding 1,000 min under continuous operation in the air. The dual-phase all-inorganic composite CsPbBr3-Cs4PbBr6 film shows attractive prospect for advanced light emission applications.

Sn-based perovskite solar cells (PSCs) have received extensive attention for photovoltaic applications. Nevertheless, the low crystallization quality of the film due to rapid crystallization results in high trap density of states, which is one of the main reasons for poor performance of Sn-based PSC devices. In this work, we developed a strategy for the formation of FASnI3 perovskites by introducing the addition of formamidine acetate (FAAc). Benefiting from the iodide-coordinated cation (FA+) and crystallization-regulated anion (AC-), FAAc could achieve the high-quality films with suppressed defects. The champion power conversion efficiency (PCE) of FAAc-modified PSC devices reached 9.96%, reserving 82% of their initial PCE of the light aging test over 1500 h. We hope that our finding could provide implications on the high-performance and stable Sn-based PSCs.

Highly efficient deep-red organic light-emitting devices (OLEDs) are indispensable for developing high-performance red-green-blue (RGB) displays and white OLEDs (WOLEDs). However, the shortage of deep-red emitters with high photoluminescence quantum yields (PLQYs) and balanced charge injection/transport abilities has severely restricted the performance of deep-red OLEDs. Herein, we design and synthesize four efficient emitters by combining the isoquinoline group with the thianthrene 5,5,10,10-tetraoxide group. Benefited from the introduction of the thianthrene 5,5,10,10-tetraoxide group, these Ir(III) complexes show improved electron-injection/-transport abilities. By enhancing the contribution of the triplet metal-to-ligand charge transfer (

Organic semiconductors combining high mobility and efficient solid fluorescence are in high demand for developing organic light-emitting transistors and electrically driven organic lasers. But, achieving such dual functional molecules is extremely challenging. In this manuscript, we report 2-phenylbenzo[g]furo[2,3-b]quinoxaline derivatives (3a–3c) and develop a new synthesis method for the furo[2,3-b]quinoxaline core. It was found that 3a exhibited favorable aggregation induced emissive enhancement behavior and reasonable hole mobility. The absolute photoluminescence quantum yield of 3a is determined to be 22.1% in solid powders and can reach a maximum of 19.7% in 50% water in THF, twice that in CH2Cl2 solution (9.2%) and dispersed in PS film (9.3%). The single crystal and thin film organic field-effect transistor of 3a show a hole mobility of 2.58 × 10−2 cm2 V−1 s−1 and 5.7 × 10−3 cm2 V−1 s−1, respectively. Our results demonstrated that the 2-phenyl-benzo[g]furo[2,3-b]quinoxaline skeleton is a promising candidate for building multifunctional organic optoelectronics.

Ligand-assisted interface engineering has been considered as a promising strategy to improve the performance and stability of perovskite solar cells (PSCs) simultaneously. Due to the insulating properties of conventional non-conjugated ligands, trap passivation is always at the expense of the interface/bulk carrier transport of the perovskite film. To overcome this paradox, a functional organic amine salt, 3-phenyl-2-propen-1-amine iodide, (PPEAI), is introduced to modify the interfacial characteristics of perovskite films via an “interfacial stitching effect”. This typical ligand could effectively contribute to the suppression of surface defects and ion migration. Furthermore, improved charge transport behavior of perovskite films can be achieved due to the conjugation and delocalization characteristics of PPEAI. By employing the optimized PPEAI modified perovskite film, a 21.01% efficiency was obtained from the champion device, with good stability under both ambient conditions and operation conditions without encapsulation.

A series of new organic emitters was prepared by introducing various donors (Ds) to the meta-position of the boron atom in the central phenyl ring in the acceptor (A) of 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (OBA). Moreover, their thermal, photophysical, electrochemical and electroluminescent (EL) properties were characterized in detail. The photophysical results revealed that these OBA-based molecules adopted a D–A configuration and exhibited efficient thermally activated delayed fluorescence (TADF) properties with a reverse inter-system crossing constant (kRISC) in the order of 105 s−1. It has been shown that introducing the –Br group to the OBA acceptor could increase kRISC by 2 to 3 times. Importantly, the deep-blue TADF emitter OBA-O showed a high photoluminescent quantum yield (PLQY) of 0.84, while its blue analog OBA-BrO with the –Br group exhibited an even higher PLQY of 0.92 in the doped film state. Benefitting from their high PLQYs as blue-emitting TADF emitters, the doped organic light-emitting diodes (OLEDs) based on these OBA-based TADF emitters exhibited attractive electroluminescent (EL) performances. The blue-emitting OLEDs with CIE (0.17, 0.17) showed the maximum external quantum efficiency (ηext) of 17.8%, current efficiency (ηL) of 33.2 cd A−1 and power efficiency (ηP) of 34.2 lm W−1, while that for the bluish-green device were 22.5%, 49.2 cd A−1 and 56.9 lm W−1, respectively. Thus, the great potential of these TADF emitter-based OBA acceptors was clearly demonstrated by their EL data. In addition, these asymmetric OBA-based molecules will enrich the structural diversity of this type of TADF emitter.

2-Phenylquinoline (PQ) and four coumarin-based ligand isomers with ease of synthesis have been selected to construct the unsymmetric heteroleptic [Ir(C1∧N)(C2∧N)(acac)]-type complex phosphors for o...

Cesium lead halide perovskites (CsPbX3) have become superior candidates for perspective optoelectronic applications. However, room temperature synthesized CsPbX3 nanocrystals (NCs) suffer from serious lattice surface traps, mostly induced by nonequilibrium reactions and polar solvent systems. Thus, direct assembly of such poor crystals cannot be available toward high efficiency light emitting diodes (LEDs). To address this issue, differing from the general post-treatment works, here we propose a double-terminal diamine bromide salts to in situ passivate the surface traps of room temperature synthesized CsPbBr3 NCs. High-quality NC solutions with photoluminescence quantum yield (PLQY) beyond 90% are obtained owing to the renovated surface bromide vacancies. Meanwhile, instead of longer oleylamine (OLA) ligand, the abridged diamine bromine ligand could significantly enhance charge transport throughout the NC film. In addition, the NC based LED performance is found related to chain length of the ligand, where the optimal luminance of 14021 Cd m−2 and current efficiency of 25.5 Cd A−1 are achieved by 1, 4-butanediamine bromide passivated NC devices. This work provides a direct efficient approach to meet the device application of room temperature synthesized perovskite NCs, underlines the significance of selective ligands to address the challenges of NC emitters in future displays and solid-state lighting.

Perovskite solar cells (PSCs) with monolayer-modified anodes are promising for high efficiency and stability devices with simplified configuration. Though preliminary studies on modified anodes by small organic molecules were reported, the goal-directed design and regulation of such compounds have been sparsely reported so far, thus limiting device performances. Herein, D-o-D type triphenylamine derivatives with non-conjugated linkage of sp3 oxygen are proposed to finely tune the energy level alignment and enhance the defect passivation at the ITO/perovskite interface, thus facilitating the efficient charge extraction at the anodes. The optimized molecules considerably ameliorate the photovoltaic performances of the corresponding inverted PSCs, engendering a preeminent power-conversion-efficiency (PCE) of 20.57% with negligible hysteresis. Remarkably, a good long-term stability is recorded for the unencapsulated device with over 94% of the initial PCE maintained after 180 days storage in N2 condition. Those improved performances validate the feasibility of the D-o-D molecules for cost-effective PSCs with high-efficiency, and excellent long-term stability.

Copper(I)-based halides are emerging as attractive nontoxic candidates to rival the lead-halide perovskites for optoelectronic applications. Herein, the zero-dimensional organic-inorganic copper halide [N(C2H5)4]2Cu2Br4 was proposed as a novel luminescence material. Its single crystals (SCs) were synthesized with a facile approach, realizing photoluminescence quantum yield (PLQY) up to 97.08% and superior stability. Importantly, TEA2Cu2Br4 SC exhibited a broadband blue emission around 463 nm with a large Stokes shift of 183 nm and a long photoluminescence (PL) lifetime up to 50 μs. In particular, the solution-processed polycrystalline films maintain a high PLQY of 94.73%. Based on temperature-dependent and time-resolved PL measurements and first-principles calculations, we propose a multi-channel phosphorescence mechanism for the broadband blue emission of this novel material. In addition, tunable PL of the polycrystalline films from sky-blue to deep-blue was realized. The solution processed electroluminescence devices employing the multiple blue emitters were readily achieved in the coordinate range of CIE from (0.15, 0.17) to (0.15, 0.04). Notably, the sky-blue EL device achieves a brightness of 85 cd/m2 and an external quantum efficiency of 0.11%. Our work thus inspires the design and synthesis of novel copper-based emitters and paves a way for future applications in white light-emitting diodes and full-color display.

Perovskite solar cells (PSCs) with inverted planar heterojunction (p-i-n) structure have attracted wide attention due to their facile preparation and flexible application. So far, poly(bis{4-phenyl}{2,4,6-trimethylphenyl}amine) (PTAA) as the hole-transport material has promised the state-of-the-art performance for p-i-n PSCs. However, the hydrophobic nature of PTAA has two contradictory impacts on the PSCs performance, namely the perfect resistance of corrosion and hygroscopicity versus the large surface-tension and incomplete surface coverage of the photoactive perovskite film. To address this challenge, an inorganic potassium fluoride (KF) buffer layer was introduced onto the PTAA substrate to regulate the surface-energy difference between PTAA and the perovskite precursor. As a result, superb quality perovskite film was synthesized. In addition, the KF treatment also downward shifts the valence-band maximum (VBM) of the polymer toward the VBM of perovskite thus facilitating the hole extraction from the perovskite to PTAA and in turn enlarging both the short-circuit current density (JSC) and open-circuit voltage (VOC) Therewith, the planar inverted perovskite solar cell aided by KF realizes a champion power conversion efficiency (PCE) of 21.51% with a JSC of 23.95 mA/cm2, VOC of 1.09V, and fill factor of 82.4%. It is also important that optimized devices exhibit excellent long-term stability, with 90% of the original PCE retained after 30 days under ambient conditions (60% humidity).

Transparent and flexible electromagnetic interference (EMI) shielding film is highly desirable due to the fast-growing flexible electronics. A silver nanowire (Ag NW) film is considered to be an ideal candidate for a transparent and flexible EMI shielding film but suffers low EMI shielding effectiveness (SE) at high transparency and poor bending durability. Herein, we introduce ferroferric oxide (Fe3O4) into a Ag NW film and demonstrate a robust EMI shielding film, which exhibits SE of 24.9 dB at 8.2 GHz and optical transparency of 90%. Fe3O4 exhibits roles of the improved absorption loss for electromagnetic radiation due to its high permeability, the enhanced reflection loss for electromagnetic radiation by increasing the conductivity of Ag NWs film, and the improved stability for the enhanced adhesion of the Ag NW EMI shielding film. Our work provides a facile method for high-performance transparent EMI shielding film, which exhibits great potential for protection for electronic devices.

The π-conjugated molecules, anthracene, pyrene and perylene with stepwise enhanced conjugation, have become a key ingredient in the design of new organic semiconductors for light emission and energy harvesting applications. Here, new biphenyl dissubstituted anthracene, pyrene and perylene derivatives are synthesized and investigated as blue-emitting materials. The designed molecules exhibited typical amplified spontaneous emission (ASE) behavior in solid thin films for the compounds dispersed in the inert polystyrene host at a rather large (5 wt%) chromophore concentration. Theoretical analysis assists in understanding the emission properties and optical gain performance. The calculations reveal enhanced transition density and increased transition dipole moment accompanying by stepwise enhanced molecular conjugation of fluorophore-cores. In addition, enhanced fluorescence quantum yield, significant shortened fluorescence lifetimes and increased radiative decay rate for designed compounds promote the occurrence of ASE behavior compared with anthracene, pyrene and perylene. As well, the vibration analysis show that the intramolecular vibrational modes of researched molecules possessed small Huang-Rhys factors, which thus bring in effective competition between radiative and non-radiative decay process in favor of optical gain. The experimental and theoretical provide evidence that the reported molecules are promising candidates for organic laser applications.

As a promising substitute for toxic lead-based perovskite, tin (Sn)-based halide perovskite has drawn much attention for photovoltaic applications. However, unsatisfied open-circuit voltage (VOC) and fill factor (FF) values of the available Sn-based perovskite solar cells (PSCs) remain a lingering cloud. In this work, we report a bilateral interfacial engineering strategy to fabricate 2D–3D bulk heterojunction Sn-based perovskite solar cells. Specifically, large cation PEAI and bifunctional LiF are evaporated at the bilateral interfaces of a FASnI3 film. The presence of PEAI improves the VOC and FF of the PSCs via improved surface coverage and the formed 2D–3D bulk heterojunction structure, while the bifunctional LiF (i) lowers the work function of PEDOT:PSS and (ii) facilitates hole extraction at the ITO/PEDOT:PSS interface. This strategy enabled a power conversion efficiency (PCE) of 6.98% with a VOC of 0.47 V and FF of 0.74. Our findings will add critical building bricks toward efficient Sn-based PSCs.

Aggregation-induced emission (AIE) materials can exhibit intense luminescence in the aggregated or solid state, which are highly desirable for OLED application. However, only limited research results on developing AIE-active PtII complexes in electroluminescence (EL) application have been reported so far. Herein, a series of AIE-active PtII(C^N)(N-donor ligand)Cl complexes have been developed. Their chemical structures have been determined by NMR, MS, and X-ray crystallography characterization. Theoretical results including the frontier molecular orbitals, the simulated UV–vis spectra, and natural transition orbitals (NTO) have been employed to insightfully interpret their photophysical properties. It has also been found that a much higher degree of molecular aggregation in these PtII complexes should be required to induce phosphorescent AIE than that for the fluorescent AIE behavior. These AIE-active PtII complexes can exhibit very strong emission in poly(methyl methacrylate) (PMMA) films with the phosph...

A series of asymmetric tris-heteroleptic Ir(III) phosphorescent complexes adopting both IrLL′L′′ (Ir3-1 and Ir3-2) and IrLL′(acac) (Ir2-1 and Ir2-2) chemical constitution have been successfully prepared, where L, L′ and L′′ represent different ppy-type (2-phenylpyridine) ligands. The IrLL′L′′ asymmetric tris-heteroleptic Ir(III) phosphorescent complexes Ir3-1 and Ir3-2 bearing three different ppy-type ligands can show better thermal stability, higher ΦP and improved ability of trapping both holes and electrons than IrLL′(acac) asymmetric analogs Ir2-1 and Ir2-2. Thanks to these advantages, Ir3-1 and Ir3-2, especially Ir3-2, can show phenomenal EL performance with a maximum external quantum efficiency (ηext) of 26.2%, a maximum current efficiency (ηL) of 88.7 cd A−1 and a maximum power efficiency (ηP) of 75.3 lm W−1, much higher than the data achieved by not only IrLL′(acac) asymmetric analogs Ir2-1 and Ir2-2, but also the traditional Ir(L)3 symmetric counterparts. To the best of our knowledge, these data represent the highest EL efficiencies ever achieved by the asymmetric ppy-type Ir(III) phosphorescent complexes reported in the literature. All these encouraging results not only indicate the great potential of the unique asymmetric IrLL′L′′ structures bearing three different ppy-type ligands in improving the EL ability of ppy-type Ir(III) phosphorescent emitters, but also represent important progress in the design and synthesis of new asymmetric ppy-type Ir(III) phosphorescent complexes with high EL ability.

Sn-based perovskite material has been selected as a strong contender for perovskite solar cells (PSCs) application compared with Pb-based perovskite, due to its more suitable bandgap and excellent optoelectronic characteristics. However, the poor quality of Sn-based perovskite film and the oxidation of Sn2+ still lead to the unsatisfactory efficiency and instability of PSCs. In our work, a type of ligand “Trifluoroethylamine iodide (3FEAI)” was developed to achieve the crystallization regulation of FASnI3 perovskite films, which could effectively improve the film quality while restricting the film defects. Moreover, it is found that the short-chain 3FEAI exhibited the better assistance of charge transport effect compared with the conventional ligand PEAI, which further contributed to the efficiency of PSCs. At last, with the introduction of 3FEAI, the prepared device shows the considerable efficiency (9.34%) and long-term stability (~10% PCE loss after 500 h of aging).

Since the emergence of organic-inorganic hybrid perovskites, the development of perovskite light-emitting diodes (PeLEDs) with green/red emission have made great progress, and the corresponding external quantum efficiency (EQE) has exceeded 20%. However, the research progress of blue-emitting PeLED still has certain challenges. In this article, a multi-cation per-bromine perovskite film is prepared by introducing polymer molecules poly(9-vinylcarbazole) (PVK) in an anti-solvent (chloroform). When the concentration of PVK is optimized to 0.1 mg/mL, a smooth, dense, high-quality film with photoluminescence quantum efficiency (PLQY) up to 20.70% is obtained. The introduction of PVK can assist the formation of perovskite films for interface modification via surface defect passivation. The optimized blue PeLED has a maximum brightness of 3136 cd/m2 and a maximum EQE of 3.49% at 488 nm. More importantly, the optimized blue PeLED has excellent color stability under high applied voltage up to 12 V or continuous operation.

Four novel fluorescent molecules based on pentavalent phosphoryl center π-conjugated heterocycles (PCCH) as acceptor have been constructed by ether, sulfide, and sulfonyl groups as tethering groups and phenoxazine or phenothiazine as the donor. Their molecular configurations, photophysical, electrochemical behaviors and electroluminescent (EL) performances have been studied. The molecular configuration of these PCCH-based emitters look like bowls, due to the bowl-shape PCCH-based acceptors. According to their special molecular structure and photophysical results, it can be concluded that the PCCH-based emitters with phenoxazyl as donors have efficient thermally activated delayed fluorescence (TADF) behavior. Interestingly, their molecular rigidity, photoluminescent quantum yield (PLQY) and TADF behaviors are correlate with the depth of the bowl in the case of the same donor. The sulfone group as tethering group into the acceptor unit among of these PCCH-based emitters exhibit optimal PL and EL performances. It has a highest PLQY of ca. 0.83, measured in doped CBP film, and the highest kRISC of 106 s−1. Importantly, its doped OLEDs can achieve exceptional EL performances with a maximum ηext of 28.2%, ηL of 90.8 cd A−1 and ηP of 83.5 lm W−1. In addition, these bowl molecules of PCCH-based emitters will enrich the structural diversity of high efficient TADF emitters.

A series of charged dinuclear Cu(I) complexes were developed by functionalization of both central bipyrimidine-based ligands and organic phosphine ligands. The chemical modification of the ligands can effectively affect the absorption, emission and thermal stability properties of the Cu(I) complexes. The decomposition temperatures ( T d ) are improved by using bulky ligands. Interestingly, the complexes with the triphenylamine group on the bipyrimidine ligand show higher photoluminescence quantum yield (PLQY) than the complexes bearing the triphenylphosphine oxide group, while the complexes having the triphenylamine group on the phosphine ligand display lower PLQY. The functional groups also show an obvious influence on the redox behaviors of these complexes. Most importantly, the organic light-emitting diodes (OLEDs) based on selected dinuclear Cu(I) complexes show impressive EL features. The best performance is achieved by the device based on complex Cu-MD-1 with the maximum external quantum efficiency (EQE) of 6.09%, current efficiency (CE) of 12.78 cd A −1 and power efficiency (PE) of 5.93 lm W −1 , representing the state-of-the-art EL efficiencies reported for the charged Cu(I) complexes. In addition, the OLEDs based on these Cu(I) complexes can emit warm white light with Color Rendering Index (CRI) as high as 88 and Commission Internationale Ed I'eclairage (CIE) coordinates close to (0.40, 0.46), showing the great potential of these Cu(I) complexes in fabricating single-emitter warm WOLEDs.

A series of cyclometalated iridium(III) complexes, Ir-B-1, Ir-B-2, Ir-B-3, and Ir-B-4, were synthesized with the 2-phenylpyridine (ppy) type main ligand possessing a dimesitylboron group and the auxiliary ligand containing other main-group element units showing unique charge injection/transporting features. Their thermal stability, photophysical and electrochemical properties, and electroluminescent (EL) performances have been characterized. Time-dependent density functional theory (TD-DFT) calculations were carried out to study the photophysical properties of these complexes. All these complexes can emit intense orange phosphorescence with extremely high quantum yields of nearly 100% measured in neat films at room temperature. Moreover, the solution-processed organic light-emitting devices (OLEDs) using these complexes as orange emitters can show very high EL efficiencies with the maximum luminance efficiency (ηL) of 85.1 cd A−1, corresponding to a power efficiency (ηP) of 69.7 lm W−1 and an external quantum efficiency (ηext) of 28.1%.

Two homoleptic thiazole-based IrIII phosphorescent emitters, Ir-3Tz1F and Ir-3Tz2F, with fluorinated 2-phenylthiazole-type ligands were designed and prepared. Their thermal stability, and photophysical and electrochemical properties, as well as electroluminescent (EL) performances in both monochromic OLEDs and solution-processed WOLEDs were investigated. When doped in monochromic OLEDs made by vacuum deposition, Ir-3Tz1F gave the maximum EL efficiencies with ηL of 56.2 cd A−1, ηext of 15.8% and ηp of 50.2 lm W−1. Critically, solution-processed WOLEDs based on Ir-3Tz1F with three primary colors could achieve an excellent trade-off among the stable balanced white EL spectra, a high EL efficiency and a high color rendering index (CRI). The optimized solution-processed WOLED exhibited very attractive EL efficiencies of 33.4 cd A−1, 16.5% and 30.6 lm W−1, while maintaining both a high CRI of ca. 80 and very stable Commission Internationale de L’Eclairage (CIE) coordinates in a wide driving voltage range from 4 V to 11 V.

Functional PtII ppy-type complexes (ppy = 2-phenylpyridine anion) with pyridine and chloride monodentate ligands are prepared, which show high electroluminescence efficiencies.

Encouraged by the high photoluminescence (PL) of the bis-ZnII salphen complexes, a series of coordination polymers have been successfully developed through metal–ligand interactions between the bis-ZnII salphen complexes and functional ditopic ligands. These bis-ZnII salphen coordination polymers can exhibit high thermal stability up to 433 °C. Their PL spectra show an emission maximum peaking at ca. 570 nm in solution and ca. 580 nm in neat films. The PL investigation of the neat films for these bis-ZnII salphen coordination polymers has indicated that the functional ditopic ligands can restrain the molecular packing among the bis-ZnII salphen units for enhancing their PL intensity. Hence, the functional ditopic ligands should exhibit great potential in avoiding exciton quenching in the emission layer formed by these bis-ZnII salphen coordination polymers in polymer light-emitting diodes (PLEDs). Benefiting from such a molecular design, these bis-ZnII salphen coordination polymers can exhibit a peak luminance (Lmax) of 8658 cd m−2, a maximum external quantum efficiency (ηext) of 3.18%, a maximum current efficiency (ηL) of 6.2 cd A−1 and a maximum power efficiency (ηP) of 4.4 lm W−1. These attractive results represent the state-of-the-art EL performances ever achieved by Schiff base ZnII coordination polymers, which would provide significant clues for developing high performance PLEDs based on Schiff base ZnII coordination polymers.

With the 9-phenyl-9-phosphafluorene oxide (PhFlOP) moiety as the acceptor (A) and various donors (D), a series of new organic emitters have been synthesized with a D-A-D configuration. Their photophysical and electrochemical behaviors and electroluminescent (EL) performances have been characterized in detail. The photophysical results have indicated that the PhFlOP-based emitters with acridyl, phenoxazyl, and phenothiazyl as donors show efficient, thermally activated delayed fluorescence (TADF) behavior, especially for the TADF emitter with the phenoxazyl donor possessing an exceptionally high rate constant of reverse intersystem crossing (

Three Ir(C∧N)2(acac)-type and one Ir(C1∧N)(C2∧N)(acac)-type coumarin-based cyclometalated Ir(III) complex isomers (IrC5, IrC7, IrC7-A, and IrC8) have been obtained using three coumarin-based isomers of 2-phenylpyridine (ppy)-type cyclometalating ligands (L-C5, L-C7, and L-C8). Two coordination isomers emerging as principal products (IrC7 and IrC7-A) are obtained in the synthesis of corresponding coumarin-based cyclometalated Ir(III) complexes because of two different coordination sites in ligand L-C7 to form a C-Ir bond. To the best of our knowledge, there are no such isomers reported to date. Interestingly, a broad range of phosphorescent color tuning from green (IrC8, λ = 516 nm) to red (IrC5, λ = 608 nm) has been realized through variation of the pyridyl substitution positions on the fused phenyl ring of the coumarin skeleton. In addition, based on natural transition orbital (NTO) analyses, features of the lowest triplet excited states (T1) from these coumarin-based cyclometalated Ir(III) complex isomers can be tuned easily by these ligand isomers as well. IrC5, IrC7, and IrC7-A show prevailing 3MLCT character associated with their T1 states which emit the phosphorescent signals, while the T1 state of IrC8 exhibits the dominant ligand-centered π-π* transition feature. Importantly, owing to the strong rigidity of the coumarin skeleton, all the coumarin-based cyclometalated Ir(III) complex isomers can show high phosphorescent quantum yields Φp (ca. 0.4-1). Together with the improved electron-injection/electron-transport (EI/ET) ability, all the phosphorescent emitters display impressive electroluminescence (EL) performance. The device based on IrC8 gives the highest EL efficiencies of external quantum efficiency (ηext) 22.7%, current efficiency (ηL) 79.7 cd A-1, and power efficiency (ηP) 58.2 lm W-1, representing the most state-of-the-art EL ability ever achieved by coumarin-based phosphorescent emitters. All these encouraging data definitely suggest the great potential of the coumarin skeleton in both easy tuning of the photophysical properties of ppy-type Ir(III) phosphorescent complexes and developing high-performance phosphorescent emitters.

The surface passivation of mid-/long-wave dual-color infrared detectors based on type-II InAs/GaSb superlattices(T2SLs) photodetectors employing diverse voltage and current conditions of sulfide treatment passivation was presented. The superlattices were grown on GaSb substrate by molecular beam epitaxy technology. The circle pixel devices in the diameter of 200 μm with 5 μm at mid-infrared and 14 μm at long-infrared 100% cutoff wavelength were fabricated. Compared to only SiO2 encapsulation passivation and unpassivated detectors, the dark current density, which takes into account surface leakage current, was reduced by approximately three orders of magnitude and the R0A-product was six times higher by sulfide treatment. Besides, detectors passivated through 22 V 15 mA sulfur treated, the responsivity of was 0.95A/W and QE was 0.44 at 2.6 μm. As for the wavelength of 5.3 μm, the responsivity and QE were 1.95 A/W and 0.45 severally.

The instability issue of Pb-free Sn-based perovskite is one of the biggest challenges for its application in optoelectronic devices. Herein, a structural regulation strategy is demonstrated to regulate the geometric symmetry of formamidiniumtin iodide (FASnI3) perovskite. Experimental and theoretical works show that the introduction of cesium cation (Cs+) could improve the geometric symmetry, suppress the oxidation of Sn2+, and enhance the thermodynamical structural stability of FASnI3. As a result, the inverted planar Cs-doped FASnI3-based perovskite solar cell (PSC) is shown to maintain 90% of its initial power-conversion efficiency (PCE) after 2000 h stored in N2, which is the best durability to date for 3D Sn-based PSCs. Most importantly, the air, thermal, and illumination stabilities of the PSCs are all improved after Cs doping. The PCE of the Cs-doped PSC shows a 63% increase compared to that of the control device (from 3.74% to 6.08%) due to the improved quality of the Cs-doped FASnI3 film.

A series of polymeric hosts with cardo-type backbone have been successfully developed with cheap palladium-free catalyst through controlling the special orientation of different monomers. By engineering the configuration of polymer backbones with different number and kind of the functional groups attached to the monomers, the triplet energy-levels (ETs) of these new polymeric hosts can be precisely controlled from 1.92 to 2.83 eV. Importantly, the functional groups on the monomers can afford improved and balanced charge carrier injection/transporting ability to these polymeric hosts. In addition, these polymeric hosts can show good thermal property with decomposition temperatures (Td) higher 410 °C and glass transition temperatures (Tg) higher than 170 °C. Benefitting from all these advanced properties, solution-processed phosphorescent organic light-emitting devices (PhOLEDs) based on these polymeric hosts can show impressive electroluminescence (EL) performances. The optimized blue device B2 possesses a maximum luminance efficiency (ηL) of 25.5 cd A−1, corresponding to a power efficiency (ηP) of 19.9 lm W−1 and an external quantum efficiency (ηext) of 11.3%. The maximum ηL, ηP and ηext for the optimized green device G2 are 66.9 cd A−1, 62.8 lm W−1 and 19.5%, respectively, while EL efficiencies of the optimized red device R2 can reach 11.0 cd A−1, 9.4 lm W−1 and 15.5%. All of the promising EL data achieved by these polymeric hosts show their great potential application in developing high performance polymer-based OLEDs.

The fill factor (FF) is a fatal parameter to determine the power conversion efficiency (PCE) of perovskite solar cells. Especially, for the large area solar cells and modules, the low FF is the bottleneck towards the high PCE. The FF is highly correlated with the carrier recombination caused by defects at interfaces. Herein, we propose that ultra-thin inorganic alkali metal fluorides interlayer passivate the interface defects by vapor evaporation method at the perovskite/electron transport layer (ETL) interface. We confirmed that the alkali metal fluorides (AF) layer can function as both defect passivation layer and physical barrier layer, showing the significant enhancement of PCE and ambient stability. Eventually, we achieve the highest FF (80.6%) for 1 cm2 size and highest FF (73.1%) for 10.8 cm2 size perovskite solar cell by potassium fluoride (KF) as passivation layer. This functional interlayer strategy paves the way to resolve the industrial requirements with low cost, high fill factor large area planar perovskite solar cells.

A cyclometalating ligand containing a 9-phenyl-9-phosphafluorene oxide (PhFlPO) moiety has been synthesized and used to construct asymmetric tris-heteroleptic cyclometalating IrIII complexes in combination with other ppy-type (Hppy = 2-phenylpyridine) ligands containing a functional group with a different charge carrier injection/transporting character. Their photophysical properties, electrochemical behaviors, and electroluminescent (EL) performances have been characterized in detail. Time-dependent density functional theory (TD-DFT) and natural transition orbital (NTO) calculation were carried out to gain insight into the photophysical properties of these complexes. The NTO results show that the characters of the lowest triplet excited states (T1) can be delicately manipulated through the combination of different cyclometalating ligands. In addition, the strong electron injection/transporting (EI/ET) ability associated with the PhFlPO moiety can confer EI/ET properties to the asymmetric tris-heterolepti...

A typical thin and fully flexible hybrid electrode was developed by integrating the encapsulation of silver nanowires (AgNWs) network between a monolayer graphene and polymer film as a sandwich structure. Compared with the reported flexible electrodes based on PET or PEN substrate, this unique electrode exhibits the superior optoelectronic characteristics (sheet resistance of 8.06 Ω/□ at 88.3% light transmittance). Meanwhile, the specific up-to-bottom fabrication process could achieve the superflat surface (RMS = 2.58 nm), superthin thickness (∼8 μm thickness), high mechanical robustness, and lightweight. In addition, the strong corrosion resistance and stability for the hybrid electrode were proved. With these advantages, we employ this electrode to fabricate the simple flexible organic light-emitting device (OLED) and perovskite solar cell device (PSC), which exhibit the considerable performance (best PCE of OLED = 2.11 cd/A2; best PCE of PSC = 10.419%). All the characteristics of the unique hybrid elec...

Down-conversion structure white organic light-emitting diodes (WOLEDs), in which white light is generated by a blue emission organic light-emitting diodes (OLEDs) in combination with a color conversion layer (CCL) outside the substrate, has attracted extensive interest due to its significant advantages in low cost and stabilized white-light emissions. However, low color-conversion efficiency of CCL is still a bottleneck for the performance improvement of down-conversion WOLEDs. Here, we demonstrate an approach to enhance the color-conversion efficiency of CCL-WOLEDs by localized surface plasmon resonance (LSPR) effect. In this approach, a blend of Ag nanoparticles and polyvinyl alcohol (PVA) is solution-deposited between the blue organic light emitting diodes and color-conversion layer. Based on the LSPR effect of this modified structure, the color conversion efficiency has improved 32%, from 45.4% to 60%, resulting a 14.4% enhancement of the current efficiency, from 9.73 cd/A to 11.14 cd/A. Our work provides a simple and low-cost way to enhance the performance of down-conversion WOLEDs, which highlights its potential in illumination applications.

We reported on the enhanced random lasing from organic dyes doped with silver nanoparticles (Ag NPs), the sizes of Ag NPs ranged from 8 nm to 250 nm. The effects of different sizes of Ag NPs on the lasing properties were studied. We found a strong dependence of the random lasing properties on the size of the Ag NPs, and the lowest threshold was achieved by the introduction of Ag NPs with the diameter of 150 nm. By studying the enhanced localized electromagnetic (EM) field due to localized surface-plasmon resonance and the scattering effect of Ag NPs in experiment and Mie theory, we found that the enhanced localized EM field plays a major role on enhanced lasing of organic dyes for the small Ag NPs (diameter

Novel N1,N3,N5-tris(9,9-diphenyl-9H-fluroen-2-yl)-N1,N3,N5-triphenylbenzene-1,3,5-triamine (TFADB) was synthesized and characterized as a hole-injecting material (HIM) for organic light-emitting devices (OLEDs). By incorporating fluorene group TFADB shows a high glass-transition temperature Tg > 168 °C, indicative of excellent thermal stability. TFADB-based devices exhibited the highest performance in terms of the maximum current efficiency (6.0 cd/A), maximum power efficiency (4.0 lm/W), which is improved than that of the standard device based on 4-4′-4″Tris(N-(naphthalene-2-yl)-N-phenyl-amino)triphenylamine (2T-NATA) (5.2 cd/A, 3.6 lm/W). This material could be a promising hole-injecting material, especially for the high temperature applications of OLEDs and other organic electronic devices.

Although organometal halide perovskite materials have shown great potential in light-emitting diodes, their performance is greatly restricted by the poor morphology of the perovskite layer. In this work, we demonstrate a facile one-step solution method to improve the perovskite film morphology via a non-solvent/solvent mixture. An efficient CH3NH3PbBr3-based light-emitting diode was prepared with a chlorobenzene/N,N-dimethylformamide mixed solvent. A high efficiency of 0.54 cd A(-1) is demonstrated, which is 22 times higher than that of a device fabricated by a traditional one-step solution process. Furthermore, the uniformity of the emission region and the device stability are strongly improved by this facile one-step solution process. Our work paves a new way for the morphological control of perovskite films for application in light-emitting diodes.