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The optical gain of blue light-emitting electrospun polystyrene fibers doped with a linear multi-fragment molecular dye based on the combination of fluorine-carbazole functional units is investigated, with the aim of correlating emission properties and the specific material architecture made of either aligned or disordered fibers. Enhanced performance is found in aligned fibers, whose gain spectrum can be finely tuned by varying the dye concentration. Instead, randomly oriented fibers show a manifold spectral line narrowing, resulting in sharp laser peaks superimposed on top of a broad emission band, ascribable to random lasing. In these systems, the increase of the dye content turns out to be effective for both decreasing the lasing threshold by about a factor 6 and for varying the laser emission wavelength. These results make these arrays and disordered architectures of fibers valuable active media for variable-gain, broadband lasing, which is remarkably important in optical sensing and tunable microlaser devices., Comment: 24 pages, 12 Figures, 1 Table, Journal of Materials Chemistry C, 2022

Using the newly designed exciplex-forming 1,2,3-triazole-based acceptors with fast and efficient singlet → triplet intersystem crossing (ISC) processes, carbazole and benzoyl-1

Using the newly designed exciplex-forming 1,2,3-triazole-based acceptors with fast and efficient singlet → triplet intersystem crossing (ISC) processes, carbazole and benzoyl-1H-1,2,3-triazole derivatives were synthesized by Dimroth-type 1,2,3-triazole ring formation and Ullmann-Goldberg C-N coupling reactions. Due to the exciplex formation between covalently bonded electron-donating (carbazole) and 1,2,3-triazole-based electron-accepting moieties with small singlet-triplet splitting (0.07-0.13 eV), the compounds exhibited ISC-assisted bluish-green thermally activated delayed fluorescence. The compounds were characterized by high triplet energy levels ranging from 2.93 to 2.98 eV. The most efficient exciplex-type thermally activated delayed fluorescence was observed for ortho-substituted carbazole-benzoyl-1H-1,2,3-triazole which was selected as a host in the structure of efficient solution-processed white light-emitting diodes. The best device exhibited a maximum power efficiency of 10.7 lm/W, current efficiency of 18.4 cd/A, and quantum efficiency of 7.1%. This device also showed the highest brightness exceeding 10 thousand cd/m2. Usage of the exciplex-forming host allowed us to achieve a low turn-on voltage of 3.6 V. High-quality white electroluminescence was obtained with the close to nature white color coordinates (0.31, 0.34) and a color rendering index of 92.

Two new asymetric D–A–D′ type compounds containing benzophenone and diphenylsulfone as electron accepting core, and acridan and thianthrene as electron donating moieties were design as multifunctional materials. The influence of different acceptor and donor units on thermally activated delayed fluorescence and room temperature phosphorescence was investigated and discussed. The combination of different donors with benzophenone unit resulted in the compound with effective frontier orbital separation, as well as the sustainment of high radiative rate. These statements are both experimentally and theoretically supported using time-resolved photoluminescence spectroscopy and DFT calculations. Deoxygenation experiment revealed higher triplet exciton contribution in the emission of benzophenone derivative, as compared to that of diphenylsulfone-based compound. The films of molecular mixtures of these emitters with 1,3-bis(N-carbazolyl)benzene demonstrated temperature-dependent photoluminescence. The estimated energy gaps between the lowest singlet and triplet states were found to be 0.06 eV and 0.27 eV for benzophenone and diphenylsulfone derivatives, respectively. Due to the relatively high singlet-triplet energy splitting of the diphenylsulfone-based compound, triplet harvesting was detected not only via temperature-stimulated fluorescence but also via room temperature phosphorescence. Displaying effect of triplet harvesting on efficiency of all-organic blue and green OLEDs based on thianthrene and acridan-substituted benzophenone or diphenylsulfone derivatives demonstrated very different maximum external quantum efficiencies of 1.4 and 22.2% respectively.

Two exciplexes were detected for the first time for the known exciplex-forming system consisting of electron donating 1,3-bis(N-carbazolyl)benzene and electron accepting 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine. Exploiting thermal treatment, sky-blue (high-energy) and orange (low-energy) exciplexes were observed for a solid-state mixture of the compounds under electrical excitation. Similarly, stable high-energy and low-energy exciplexes were observed for new exciplex-forming systems consisting of 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine and one of four selected carbazole and fluorene hybrid trimers as donors. The high-energy exciplexes were observed when there was a small energy barrier between the locally excited state and the high-energy exciplex state. A large energy barrier between the locally excited state and the low-energy exciplex state was the reason that the dual nature of exciplexes was not discovered yet. Emission of both exciplexes was observed in electroluminescence spectra of exciplex-interface based devices using developed exiplex-forming systems as emitters. Observed under optical and electrical excitations, the low-energy exciplexes were separated using thermal treatment of the studied exciplex-forming systems. The exciplex-forming system consisting of 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine and 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole, which exhibits thermally activated delayed fluorescence, showed the best performance in organic light-emitting diodes (OLEDs) based on interface and volume exciplex emitters. The best device showed maximum external quantum and maximum current efficiencies of 18% and 54 cd A−1 respectively. Additionally, white OLEDs were fabricated exploiting sky-blue and orange emissions from a single exciplex-forming system. Our findings provide evidence of the dual nature of exciplexes and pave the way towards design of new exciplex-forming systems with high photoluminescence quantum yields and efficient exciplex-based devices.

New derivative acridan and isophthalonitrile (DAcIPN) was designed and synthesized as efficient TADF-type emitter with photoluminescence quantum yield of doped solid-state layer reaching 83%. Tuning of emission and efficiency of TADF emitter was performed by controlling the singlet-triplet energy splitting. Three important effects concerning the solid-state photophysics of TADF emitter was observed and analyzed, providing deep insight on the following new- or opposed-to-established results: (i) the TADF efficiency of DAcIPN in guest-host mixtures is insensitive to the host polarity; (ii) aggregation and (iii) annealing processes were found to respectively reduce and increase the dihedral angle between isophthalonitrile ring and acridan moiety, with strong impacts on the photoluminescence parameters. Thermal annealing of DAcIPN-based systems helps both the diffusion of DAcIPN molecules towards a better phase mixing (disaggregation), and the molecular geometry relaxation towards larger dihedral angles. Organic light-emitting diodes with smaller degree of aggregation of DAcIPN demonstrate outstanding lighting characteristics: brightness of 20700 (at 8 V) and 44900 (at 11 V) cd/m2, maximum current, power and external quantum efficiencies of 68 and 63 cd/A, 62 and 33 lm/W, 22.5 and 17.1%, for green and yellow devices respectively.

Four new derivatives of thianthrene and phenothiazine are reported as emitters for oxygen sensing. They exhibit both fluorescence and phosphorescence at room temperature. Effects of the substitution pattern of phenothiazine moiety on the thermal, electrochemical, emissive and oxygen sensing properties of the compounds are discussed. No phosphorescence at room-temperature was detected for deoxygenated solutions of the compounds. Room temperature phosphorescence of the different intensity was detected for the compounds being in crystalline or amorphous phase and for their dispersions in different polymeric matrices. Fast oxygen response (ca. 0.1 s) of room temperature phosphorescence was observed for only 1 wt.% of the dispersions in polymeric host. The highest oxygen sensitivity, was demonstrated for methylphenothiazinyl-disubstituted thianthrene dispersed in poly(methyl methacrylate). Stern-Volmer constant of 21·10−4 ppm−1 was obtained compared to those of 0.97·10−4, 1.22·10−4 and 2.1·10−4 ppm−1 observed for the dispersions of other compounds. Displaying possibility of oxygen detection by different chromaticity responses of emission of the developed compounds, strong yellowish-green emission with CIE1931 coordinate of (0.294, 0.503) was observed for one sample in the absence of oxygen; while, weak deep-blue emission with CIE1931 coordinate of (0.174, 0.141) was observed for the same sample in oxygen atmosphere.

New donor-acceptor and donor-acceptor-donor compounds based on perfluorobiphenyl electron acceptor and diphenylamine or carbazole as electron-donating units were designed, synthesized and characterized. The influence of the nature and number of electron-donating units on thermal, electrochemical and photophysical properties was studied. The compounds exhibited photoluminescence ranging from near-UV to green region. The solid samples of the compounds demonstrated photoluminescence quantum yields in the range from 0.1 to 0.51.2,7-Dimethoxycarbazole-containing compound was characterized by negligible energy gaps between the lowest singlet and triplet states (0.1 eV) and subsequently showed thermally activated delayed fluorescence (TADF). Carbazolyl-substituted perfluorobiphenyl derivatives showed aggregation-induced emission enhancement and high values of the energies of triplet levels (up to 3.08 eV). The derivatives exhibited from moderate to high temperatures of 5% weight loss up to 356 °C. Electron mobility up to 1.2 × 10−4 cm2 V−1 s−1 at electric field of 7 × 105 V/cm was detected for the studied compounds by time-of-flight measurements. One compound with the best combination of the required properties for the OLED hosts was selected for the fabrication of green TADF-based OLED. The device showed maximum external quantum efficiency of 15.1%. Another compound exhibiting efficient TADF demonstrated oxygen sensitivity with non-linear Stern-Volmer curve which was well fitted by two Stern-Volmer constants of 6.54·10−4 and 7.17·10−6 ppm−1.

The derivatives of carbazole and tetraphenylethylene exhibiting aggregation-induced emission and 4,4′,4′-tris[3-methylphenyl(phenyl)amino]triphenylamine were used for the preparation of organic light-emitting diodes the electroluminescence spectra of which include exciton and exciplex emissions. The low-energy exciplex emission of the electroluminescence spectrum was formed at the interface of the emissive layers. The best fabricated device showed turn-on voltage of 2.7 V for electroluminescence (at 10 cd/m 2 ); maximum current efficiency of 11.5 cd/A, maximum brightness of 17,700 cd/m 2 (at 11 V), and external quantum efficiency of ca. 3.9% with CIE 1931 chromaticity coordinates (0.20, 0.38).

Cationic polymerization of two styrene derivatives containing carbazole moiety with different linking topology, 9-(4-vinylphenyl)carbazole (M1) and 3-(4-vinylphenyl)-9-ethylcarbazole (M2), using 1-chloro-1-phenylethane (PhEtCl)/SnCl4 initiating system has been investigated. It was shown that polymerization of M1, which is characterized by higher electron density on the carbon at the 3 position of carbazolyl group than on vinyl group, proceeds predominantly via step-growth (SG) pathway through addition of protonated monomer/oligomers to 3-position of carbazolyl group (electrophilic aromatic substitution). On the contrary, M2, in which 3-position of carbazolyl group is protected via introduction of 4-vinylphenyl group, polymerized predominantly via chain-growth (CG) pathway through addition of carbocation to double bond of monomer. The polymers synthesized via SG mechanism showed different photophysical characteristics in comparison with corresponding monomer, while in case of polymers prepared via CG mechanism the polymer and monomer have the same absorption and fluorescence profiles.

New tri- or tetraphenylethylene-substituted phenylcarbazole derivatives exhibiting aggregation-induced emission were synthesized by the synthetic route including Pd-catalyzed Suzuki or Buchwald-Hartwig coupling and Heck reactions. The results of evaluation of the thermal, optical, electrochemical, photophysical, and charge-transporting properties of the synthesized derivatives are presented. The compounds possess high thermal stabilities with 5% weight loss temperatures exceeding 350 °C. Some of the synthesized compounds form glasses with glass transition temperature ranging from 77 to 114 °C. Their maximum fluorescence intensity wavelengths are in the range of 472–498 nm. The highest photoluminescence quantum yield of 43.9% was observed for the solid sample of 2-(4-(4-(1,2,2-triphenylvinyl)phenylethenyl)phenyl)-9-ethylcarbazole. The electron photoemission spectra of the films of the synthesized compounds revealed ionization potentials of 5.49–5.74 eV. Hole drift mobilities in the layers of 9-phenylcarbazole para-substituted with tri- or tetraphenylethylene moities reached 10−3 cm2 V−1 s−1 at moderate electric fields, as established by the time-of-flight technique.

New carbazole-based monomers with two reactive functional groups such as epoxypropyl, oxetanyl and vinyloxethyl were synthesized and their cationic photopolymerization was performed. The monomer containing epoxypropyl groups exhibited the highest conversion in photopolymerization (78%). The monomers and polymers exhibited ability of glass formation with the glass transition temperatures up to 98 °C for low-molecular-weight compounds and those observed for polymers ranging from 89 to 150 °C. The synthesized derivatives absorb electromagnetic irradiation in the range of 200–390 nm with the band gaps of 3.14–3.16 eV. The compounds exhibit blue photoluminescence with the intensity maxima at 400 nm. The compounds were found to have high triplet energies of ca. 2.78 eV. The electron photoemission spectra of the layers of the synthesized compounds revealed ionization potentials of 5.20–5.37 eV. The time-of-flight hole drift mobilities of the layers of the compounds exceed 10 − 5 cm 2 /V × s at high electric fields.

The anionic ring-opening polymerization of carbazole-containing monomers, (9-carbazolylmethyl)thiirane (M1) and (3,6-di-tert-butyl-9-carbazolylmethyl)thiirane (M2), with hexanethiol or pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) as initiators and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst at 20 °C in tetrahydrofuran or N,N-dimethylformamide as solvents has been studied. The polymerization of these monomers proceeds in a living fashion affording linear and star-shaped polymers with controlled molecular weight (Mn = 4000–15,000 g mol−1) and relatively low polydispersity (Đ

A series of twisted-structure carbazole–fluorene tetrads featuring 3,3′-bicarbazole core decorated with singly-bonded carbazole and fluorene end-linkers were synthesized and studied as potential host materials. The tetrads inferred high glass transition temperature (up to 105 °C) and good film-forming properties, which contributed in attaining large hole drift mobilities (up to 10−3 cm2/V/s) in the solution-processed amorphous films. The revealed high triplet energies (up to 2.9 eV) indicated their potential to be utilized as hosts in blue light-emitting devices. Greater sensitivity of the triplet energies to the linking position of peripheral moieties as compared to the sensitivity of the singlets imply new possibilities for the independent tuning of these energies in carbazole–fluorene tetrads.

The impact of linking topology of fluorene-carbazole triads on amplified and spontaneous emission as well as on concentration quenching of emission and charge carrier mobility, i.e. on the properties essential for organic laser application, was investigated. Deep-blue-emitting triads featuring 2,7- substitution pattern and bulky alkyl moieties expressed high emission quantum yield (0.8–0.9) and low concentration quenching, which benefited in attaining large radiative decay rates (∼109 s−1) and rather low amplified spontaneous emission (ASE) threshold (down to 9 kW/cm2) for compound concentrations up to 3 wt % in polymer matrix. Most of the triads expressed carrier drift mobilities close to 10−2 cm2/(V·s) in amorphous films pointing out efficient charge transport essential for reducing threshold current density for lasing. The impact of the position (central or side) of fluorene/carbazole moieties in the triad or the linking position (C-2 or C-3) of the side groups on the ASE threshold and carrier mobility was found to be of little significance. However, a huge advantage of 2,7- substitution pattern over 3,6- pattern for the triads in terms of ASE performance was demonstrated. Importantly, the obtained results suggested a possible trade-off between ASE threshold reduction and carrier mobility enhancement, which may hamper the realization of electrically-driven lasing in organic amorphous films.

The star-shaped compound tri(9-hexylcarbazol-3-yl) amine (THCA) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were used for the preparation of bilayer and bulk exciplex based organic light emitting diodes (OLEDs) in which THCA and Bphen were selected as donor and acceptor components, respectively. The dependencies of the electroluminescence and impedance characteristics of the exciplex type OLEDs depending on the technologies of the formation of the active layers were studied. The correlations between the appearance of negative differential resistance in current–voltage characteristics and negative capacitance observed at low frequencies in impedance spectra of OLEDs with the resonant tunneling of electrons into THCA through Bphen/THCA barrier and generation–recombination processes in THCA were established.

In the field of materials for optoelectronic applications much attention is paid to the derivatives of triphenylamine and carbazole. We report on the electrochemical and spectroelectrochemical properties of two conductive polymers prepared by electropolymerization of two compounds containing either carbazole or triphenylamine moieties. Electrochemical, UV Vis- and EPR-spectroelectrochemical tools were used to study the properties of the polymers. The basic characteristics such as the band gaps, HOMO and LUMO values, absorption and emission maximum wavelengths of the monomers and the polymers are reported and discussed.

We fabricated a yellow organic light-emitting diode (OLED) based on the star-shaped donor compound tri(9-hexylcarbazol-3-yl)amine, which provides formation of the interface exciplexes with the iridium(III) bis[4,6-difluorophenyl]-pyridinato-N,C2']picolinate (FIrpic). The exciplex emission is characterized by a broad band and provides a condition to realize the highly effective white OLED. It consists of a combination of the blue phosphorescent emission from the FIrpic complex and a broad efficient delayed fluorescence induced by thermal activation with additional direct phosphorescence from the triplet exciplex formed at the interface. The fabricated exciplex-type device exhibits a high brightness of 38 000 cd/m(2) and a high external quantum efficiency.

Isomeric 3,6-dimethoxy- and 2,7-dimethoxycarbazoles containing diphenylethenyl moieties were synthesized by condensation of the appropriate dimethoxycarbazoles with diphenylacetaldehyde. The solid-state structures and the molecular order of the compounds were proven by X-ray crystallography. Both compounds were found to be capable of glass formation with comparable glass transition temperatures (70–71 °C). They exhibited high thermal stabilities, with the 5% weight loss temperatures exceeding 375 °C. The isomer having diphenylethenyl groups at C-3 and C-6 positions and methoxy groups at C-2 and C-7 positions (3a) exhibited aggregation-induced emission (AIE), while its counterpart having diphenylethenyl groups at C-2 and C-7 positions and methoxy groups at C-3 and C-6 positions (3b) showed the opposite effect, i.e. aggregation-caused quenching (ACQ). The derivative 3b showed superior charge transporting properties. Time-of-flight hole drift mobilities in its layers approached 10−3 cm2 V−1 s−1 at high electric fields. A comparative theoretical analysis of the compounds was performed using density functional theory (DFT) and time-dependent DFT calculations. They proved more effective π-conjugation in the derivative of 3,6-dimethoxy carbazole (3b), which was also observed by UV and fluorescence spectroscopies. The theoretical study revealed relatively low ground state dipole moment of 0.69 D of the isomer 3b, while its counterpart (3a) showed much higher ground state dipole moment of 5.98 D. The difference in polarity was found to have the crucial effect on the molecular arrangement in the crystals and consequently, on the thermal transitions and charge-transporting properties.

Random lasers are based on disordered materials with optical gain. These devices can exhibit either intensity or resonant feedback, relying on diffusive or interference behaviour of light, respectively, which leads to either coupling or independent operation of lasing modes. We study for the first time these regimes in complex, solid-state nanostructured materials. The number of lasing modes and their intensity correlation features are found to be tailorable in random lasers made of light-emitting, electrospun polymer fibers upon nanoparticle doping. By material engineering, directional waveguiding along the length of fibers is found to be relevant to enhance mode correlation in both intensity feedback and resonant feedback random lasing. The here reported findings can be used to establish new design rules for tuning the emission of nano-lasers and correlation properties by means of the compositional and morphological properties of complex nanostructured materials., 30 pages, 10 figures

Two new carbazole-containing aromatic imides were synthesized by three-step synthetic pathway with the moderate yields up to 76%. The compounds were investigated theoretically. TD-DFT computational studies revealed low singlet-triplet energy differences. The compounds were found to have relatively high thermal stability with 5% mass loss temperatures in the range of 280–310 °C. Phthalimide-based compound exhibited aggregation-induced emission enhancement and thermally activated delayed fluorescence with photoluminescence quantum efficiency of 20% in the solid state. Structure-properties relationship of this compound was investigated and it was found that charge-transfer through space mechanism is responsible for the emission. Series of green-emitting doped and non-doped electroluminescent devices were fabricated based on the carbazole-phthalimide derivative were fabricated to reveal best-performing mCP-doped device demonstrating maximum external quantum efficiency of 2.4% with current efficiency of 6.6 cd/A and power efficiency of 4.0 lm/W with maximum brightness of 8300 cd/m2.

A three-terminal organic light-emitting device with a periodic interrupted middle electrode is developed to allow for an adjustable emission color. The emission results from three independent light-emitting diodes with one diode utilizing exciplex emission. An equivalent electrical circuit is suggested taking the current–voltage characteristics and the direction of current flow through the organic structure into account. Two diodes are formed between the embedded middle electrode and the LiF/Al top and ITO bottom electrode, respectively, and the third diode utilizes that part of the device without the middle-electrode exhibiting exciplex emission. It will be shown that the spectrum of the emitted light can be tuned from blue to orange by controlling the applied potentials to the device terminals.

The starburst carbazole derivative and phosphorescent bis-cyclometalated iridium(III) complex (IC2) were used for the preparation of multilayered “warm-white” organic light-emitting diodes (OLEDs), the emission spectra of which are modulated by the thickness of the phosphorescent layer. It was shown that the electroluminescence spectra of the fabricated devices are more extended into the visible region compared with the photoluminescence spectra of both component materials. The observed extension of the electroluminescence spectra can be assigned to the phosphorescent emission of the low-energy exciplex formed at the interface of the emissive layers. The quantum-chemical calculations performed by the DFT and (TD) DFT methods support the formation of the low-energy triplet exciplex at the interface of the IC2 layer and the neighboring layer of the starshaped carbazole-based compound, (4,4′,4″-tris[3-methylphenyl(phenyl)amino] triphenylamine, tri(9-hexylcarbazol-3-yl)amine (THCA). Indeed, the triplet excite...

New star-shaped derivatives of 10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazole (triindole) with reactive functional groups are synthesized. Triindole monomers were found to have similar profiles of absorption and fluorescence spectra due to the presence of the same chromophore. The ionization potentials of the monomers are found to be comparable (5.37–5.53 eV). Hole drift mobilities of the amorphous layers of oxetane and vinyl ether molecularly dispersed in bisphenol Z polycarbonate (50%) exceed 10−5cm2/Vs at high electric fields. Cationic photocross-linking of triindole containing oxirane, oxetane and vinyl ether initiated with diphenyliodoniun tetrafluorborate is carried out.

The properties of the pyrenyl-substituted fluorene and carbazole compounds exhibiting charge carrier transport properties are reported. Cyclovoltammetric experiments revealed the electrochemical stability of the fluorene compounds. In contrast to the fluorene derivatives, the carbazole compounds showed nonreversible oxidations in the CV experiments. The pyrene-substituted fluorene and carbazole derivatives showed capability of transporting holes as characterized by xerographic time of flight technique. Ionization potential values measured by electron photoemission spectroscopy were found to be in the range of 5.70 eV – 5.93 eV.

We have found that the structures based on ITO/tri(9-hexylcarbazol-3-yl)amine/Ca/Al fabricated by means of vacuum deposition generate acoustic oscillations when pulse voltage is applied. Impedance spectroscopy study indicates the presence of significant inductive response, which is the result of significant energy barriers at the semiconductor-metal interface. We assume that a very heterogeneous spatial distribution of the electric field at the organic/metal interface and the noncoplanarity of the molecules cause the electrostriction effect in the structures.

Twin derivatives with two 9-alkylcarbazol-3-yl fragments were synthesized by the multi-step synthetic rout. The materials were characterized by differential scanning calorimetry and electron photoemission technique. Some of the electro-active derivatives were tested as solution processed hole transporting layers in organic light-emitting diodes with Alq(3) as the emitter. The electroluminescent devices exhibited promising overall performance with a maximal photometric efficiency of about 2.9 cd/A and maximum brightness of 6000 cd/m(2). (C) 2013 Elsevier B.V. All rights reserved.

We demonstrate the fabrication and properties of an near ultraviolet organic light emitting diode (UV OLED) that contains 2,7-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole organic emitting layer and aluminum-doped magnesium zinc oxide (ZnMgO:Al) layer as transparent electrode. The obtained ZnMgO:Al layer is transparent for the wavelengths longer than 325 nm and has low resistivity of the order of 10-3 Ωcm. The UV OLED device turns on at the applied voltage of 9 V.

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/m2 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/m2 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).

Synthesis and properties of new dimethyldiphenylamino-substituted carbazoles are reported. A comparative experimental analysis of 2-, 2,7-substituted carbazole derivatives and 3-, 3,6-substituted analogues is performed. Disubstituted carbazole derivatives exhibit more than 2-fold higher glass transition temperatures (99–100 °C) as compared to the monosubstituted compounds (38–40 °C). Dilute solutions of the dimethyldiphenylamino-substituted carbazole compounds are found to emit in the blue region with the fluorescence quantum yield of up to 0.45. More symmetrical molecular geometry of the 2-, 2,7-substituted carbazole compounds favors closer molecular packing in the neat films thereby facilitating exciton migration and migration induced exciton quenching, which results in the significantly reduced excited state decay times (down to sub-nanoseconds) and fluorescence quantum yields (down to 0.04). The 2-, 2,7-substituted carbazole compounds are shown to demonstrate the superiority over 3-, 3,6-substituted compounds by giving rise to extended π-conjugation and expressing over one order of magnitude higher radiative decay rates. The synthesized compounds are electrochemically stable: their cyclic voltammograms show reversible oxidation behavior. The ionization energies of the synthesized compounds are in the range of 5.16–5.28 eV. Hole drift mobilities of the molecular mixtures of dimethyldiphenylamino-substituted carbazoles with bisphenol Z polycarbonate reach 10 −5 cm 2 V −1 s −1 at high electric fields.

New pyrenyl mono- and disubstituted fluorene and carbazole derivatives were synthesized and investigated as blue-emitting materials. Most of the synthesized compounds were capable of forming glasses with glass transition temperatures up to 105 °C. The mono- and disubstituted compounds exhibited efficient emission in a diluted form with the peak wavelengths of 416 and 422 nm and quantum yields of 0.72 and 0.82, respectively. Photophysical properties of the compounds in dilute solutions and solid state were investigated experimentally and rationalized by density functional theory calculations. The calculations revealed a low energy barrier for intramolecular twisting in the ground and excited states. The electronic spectra of the compounds were dominated by an allowed “pyrene-like” S0 → S2 transition prevailing in nearly perpendicularly twisted molecular structures and competitive S0 → S1 transition becoming increasingly allowed for more planar conformers. The disubstituted compounds demonstrated a 3-fold e...

The synthesis of a series of carbazole-based monomers incorporating dibenzazepines at the 3 position is reported. Full characterization of their structures is presented. The monomers were subjected to cationic polymerization using BF 3 ·O(C 2 H 5 ) 2 as an initiator. The synthesized low-molar-mass compounds and oligomers were examined by differential scanning calorimetry, UV spectrometry, electron photoemission and time of flight techniques. The electron photoemission spectra of the films of synthesized materials revealed the ionization potentials of 5.12–5.34 eV. Hole drift mobilities of low-molar-mass compounds molecularly dispersed in bisphenol Z polycarbonate range from 2.6 × 10 −8 to 1.7 × 10 −6 cm 2 /V s at high electric fields as it was established by xerographic time of flight technique.

The synthesis of a series of 2-(10,11-dihydrodibenz(b,f)azepinyl)carbazole-based monomers is reported. Full characterization of their structures is presented. The monomers were subjected to cationic polymerization using BF3·O(C2H5)2 as an initiator. The synthesized monomers and polymers were examined by differential scanning calorimetry, UV spectrometry, cyclic voltammetry and electron photoemission spectrometry. The electrochemical investigation of the solutions of the synthesized compounds revealed HOMO values ranging from −5.12 to −5.06 eV. Electron photoemission spectrometry of the solid samples gave ionization potentials of 5.40–5.50 eV.

The electroluminescent device ITO/CuI/3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole(TCz1)/Ca/Al in which TCz1 for the first time was used as the emitting layer, was fabricated by means of vacuum deposition. The device emits blue light with a peaks at 388 and 406 nm at 4.5 V, with high current efficiency values (11.5 cd/A) and external quantum efficiency (1.72%).

The synthesis and properties of carbazole and diphenylamine derivatives with different numbers and positions of methoxy groups in the diphenylamino moiety are reported. A comparative study on their thermal, optical, and photoelectrical properties is presented. All the synthesized compounds are found to form glasses with the glass transition temperatures in the range of 39−69 °C, as characterized by differential scanning calorimetry. The ionization potentials of the synthesized compounds were estimated both theoretically by quantum chemical calculations and experimentally by an electron photoemission in air technique. The trends observed by theoretical calculations are confirmed by experimental results. The experimental values of ionization potentials range from 5.10 to 5.56 eV. Compounds containing monomethoxy-substituted phenyl rings exhibited lower ionization potentials than compounds containing di- and trimethoxy-substituted phenyl moieties. The highest ionization potential was observed for the compoun...

Synthesis and properties of new glass-forming 2-, 2,7-substituted carbazole dimers and trimers exhibiting ambipolar charge carrier transport are reported. The results of thorough evaluation of thermal, optical, and photoelectrical properties of the carbazole derivatives are presented. Additionally, a comparative experimental and theoretical analysis of the 2,7-substituted carbazole trimer with the 3,6-substituted analogue is performed. 2,7-Di(9-carbazolyl)-9-(2-ethylhexyl)carbazole was found to show very high electron mobility (μe = 2 × 10−3 cm2 V−1 s−1 at an electric field of 1.8 × 105 V/cm) and reasonably high hole mobility (μh = 8 × 10−4 cm2 V−1 s−1 at an electric field of 1.8 × 105 V/cm). 2-Substituted carbazole dimers also demonstrate bipolar conductive properties although with significantly lower charge carrier mobility values. The obtained carrier mobility values for the 2,7-substituted carbazole compound were found to be nearly 2 orders of magnitude higher than those for 3,6-substituted carbazole ...

The synthesis and properties of hole-transporting triaryl diamine-based low-molar-mass compounds and polymer are reported. Comparative study on their thermal, optical, and photoelectrical properties is presented. All the synthesized compounds are found to form glasses with the glass transition temperatures in the range of 43–119 °C as characterized by differential scanning calorimetry. The ionization potentials of these compounds range from 5.31 to 5.40 eV as determined by electron photoemission method. Hole-drift mobilities in the films of the synthesized compounds were estimated by the xerographic time-of-flight technique. They were found to reach 10−3 cm2/Vs at electric field of 6.4 × 105 V/cm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4674–4680, 2008

Synthesis and properties of fluorene and carbazole derivatives having three electrophores per molecule with different architectures are reported. The synthesized compounds possess high thermal stabilities with 5% weight loss temperatures exceeding 350 °C. They form glasses with glass transition temperatures ranging from 60 to 68 °C. Cyclovoltammetric experiments revealed the high electrochemical stability of the fluorene trimer. In contrast, 2- and 2,7-fluorenyl substituted carbazole derivatives show irreversible oxidation in the CV experiments. The electron photoemission spectra of the films of the synthesized compounds revealed ionization potentials of 5.65-5.89 eV. Hole drift mobilities in the amorphous layers of the synthesized compounds reach 10(-2) cm(2) V(-1) s(-1) at high electric fields, as established by a xerographic time-of-flight technique. DFT calculations show that HOMO and LUMO orbitals of the compounds are very similar in energy and shape. The similar hole mobilities observed for the three compounds are discussed in the frame of the Marcus theory. An important influence of the alkyl groups on the ionization potentials and on the hole mobilities was also observed and its origin is discussed.

International audience; Two new star-shaped carbazole molecules, including tri(9-(methoxyphenyl)carbazol-3-yl)amine named TMPCA having molecular glasses properties and hole transport properties were synthesized. Their thermal, optical, photophysical and electrochemical properties were studied. The carbazole based molecules exhibit high thermal stability with 5% weight loss temperatures over 480 °C with higher glass temperature transitions 164-175 °C than the classical spiro-OMeTAD reference molecule. Their optical band gaps (2.76 eV) are low enough not to hinder neither the absorption of the indoline sensitizer (D102) nor its photoexcitation and charge transfer. Solid state ionization potential (IPs) of TMPCA is well adapted to that of D102 and ensure a driving force ΔrG >0.2 eV for an efficient transfer and regeneration of the photo-oxidized dye. Solid-state dye sensitized solar cells ITO/TiO2/D102/T4MPCA/Au showed a power conversion efficiency of 2.23% with Jsc of 8.85 mA cm−2 under standard AM 1.5 simulated solar irradiation.

International audience; Efficient molecular glasses based on carbazole moiety used as hole transporting materials were synthesized. The role of the mono- or di-substitution of dimethoxy-diphenyl amine groups on the 3 and/or 6 position of the carbazole was evidenced. Their thermal, optical, photoelectrical, electrochemical properties as well as their photovoltaic characteristics on solid-state dye sensitized solar cells were investigated. The performance of these materials in solid-state DSSC based on TiO2 sensitized with the commercial indoline organic dye D102 is widely discussed. In such configuration, a power conversion efficiency of 3.4% and a fill factor of 0.53 are achieved with a 3,6-substitued carbazole molecular glass derivative, under standard AM 1.5 simulated solar irradiation. In addition, the Jsc value is even higher than the spiro-OMeTAD, due to its higher mobility. These results are found to be very promising since no specific optimization was performed on the devices yet. By comparison, the corresponding reference device incorporating spiro-OMeTAD as p-type organic semiconductor gives similar power conversion efficiency of 3.5%, showing the relevance of our approach.

Diphenilamino-substituted carbazoles were used as guest compounds for the preparation of highly efficient blue organic light-emitting diodes based on the phenomenon of delayed fluorescence. It was shown that the spectra of the delayed fluorescence of host–guest systems are identical to those of the prompt fluorescence and in general coincide with the photoluminescence spectra of the guest films. The congruence of the prompt and delayed fluorescence spectra is explained by the effective intermolecular triplet–singlet (T → S) energy transfer from the excited T states of the host to the S states of the guest molecules. High external electroluminescence efficiency of the fabricated electroluminescent devices, reaching 17%, is comparable to that achieved in phosphorescence-based organic light-emitting diodes.

a b s t r a c t The synthesis and properties of glass-forming diphenylamino-substituted derivatives of 9- phenylcarbazole with methoxy groups in the different position of diphenylamino moieties are reported. A comparative study on their thermal, optical, photoelectrical and electrochemical properties is presented. The synthesized compounds exhibit high thermal stability with 5% weight loss temperatures ranging from 344 to 475 ◦C. The derivatives absorb electromagnetic irradiation in the range of 225-425 nm with the band gaps of 2.94-3.08 eV. The ionization energies of the synthesized compounds range from 5.04 to 5.56 eV. The lowest ionization energies and band gaps are observed for compounds containing para methoxy-substituted phenyl rings of diphenylamino moieties and for disubstituted carbazole derivatives. Charge-transporting properties of the selected compounds were tested by time-of-flight technique. Hole drift mobilities in the amorphous layers of the materials reach 10−3 cm2/V s at high electric fields. The derivatives were tested as hole transport materials in solid-state dye sensitized solar cells and showed conversion efficiency up to 0.54%. © 2012 Published by Elsevier B.V.

International audience; A comparative study of thermal and electrochemical properties of 2,7 and 3,6 disubstituted carbazole is presented and their performances were compared in solid state Dye Sensitized Solar Cell (DSSC). Although the two compounds possess similar glass transition temperature of 100°C, their electrochemical behaviors are quite different. HOMO energy levels have been evaluated at -4.7 eV and -5.1 eV respectively for 2,7 and 3,6 disubstituted carbazole derivatives. Incorporated as hole transporting materials in solid state DSSC, the 2,7 carbazole exhibits an efficiency conversion of 0.18 % while the 3,6 carbazole gives 0.34 % of efficiency conversion due to a better pore filling in the mesoporous TiO2

We demonstrate the fabrication and properties of an near ultraviolet organic light emitting diode (UV OLED) that contains 2,7-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole organic emitting layer and aluminumdoped magnesium zinc oxide (ZnMgO:Al) layer as transparent electrode. The obtained ZnMgO:Al layer is transparent for the wavelengths longer than 325 nm and has low resistivity of the order of 10−3 Ωcm. The UV OLED device turns on at the applied voltage of 9 V.

Cataloged from PDF version of article. The results of an experimental study of the electroluminescent device made of ITO/CuI/2,6-di-tert-butyl-4-(2,5-diphenyl-3,4-dihydro-2H-pyrazol-3-yl)-phenol (HPhP)/3,6-Di(9-carbazolyl)-9-(2ethylhexyl) carbazole (TCz1)/Ca:Al with efficacy up to 10.63 cd/A are presented. HPhP provides blue emission with a peak wavelength at 445 nm. The layer of TCz1 acts as an electron-transporting layer. In the framework of density functional theory (DFT) approach the geometry configuration and energy levels of HPhP are found being in a good agreement with spectral and cyclic voltammogram data. (C) 2011 Elsevier B.V. All rights reserved.

2,7-Di(9-carbazolyl)-9-(2-ethylhexyl)carbazole was synthesized and investigated as new effective hole-transporting material. The synthesized compound showed high thermal stability with the initial weight loss temperature of 400 °C. It forms glass with glass-transition temperature of 88 °C. Hole drift mobilities in the amorphous films of the newly synthesized compound exceeded 10-2 cm 2 V- 1 s- 1 at high electric field, as characterized by the xerographic time of flight technique.