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Selfa??assembled Helical Arrays for Stabilizing the Triplet State
摘要： Room-temperature phosphorescence of metal and heavy atom-free organic molecules has emerged as an area of great potential in the recent past. A rational design played a critical role in controlling the molecular ordering to impart efficient intersystem crossing and stabilize the triplet state to achieve room-temperature ultralong phosphorescence. However, in most of the cases, the strategies followed to strengthen phosphorescence efficiency have resulted in a reduced lifetime, and the available nearly degenerate singlet-triplet energy levels impart a natural competition between delayed fluorescence and phosphorescence, with former one having the advantage. Here, an organic helical assembly supports it towards phosphorescence in this competitive pathway to exhibit an ultralong phosphorescence lifetime. In contrary to other molecules, 3,6-phenylmethanone functionalized 9-hexylcarbazole exhibits a remarkable improvement in phosphorescence lifetime (> 4.1 sec) and quantum yield (11 %) due to an efficient molecular packing in the crystal state. A right-handed helical molecular array act as a trap and exhibits triplet exciton migration to support the exceptionally longer phosphorescence lifetime. The present work will urge new molecular designs to achieve ultralong organic phosphorescence under ambient conditions.
关键词： ultralong phosphorescence,phenylmethanone,carbazole,waveguiding,helicity
更新于2025-09-23 15:21:01
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Design, Synthesis and Application of Imidazole-Based Organic Dyes in Dye Sensitized Solar Cells
摘要： Metal-free D–D–p–A type dyes (i.e., Car-Cy, Car-Rh, Dpa-Cy, and Dpa-Rh) were designed and synthesized for dye-sensitized solar cells (DSSCs). In the structure of the sensitized dyes, an imidazole ring is connected to a carbazole or diphenylamine moiety as a donor while cyanoacetic acid or rhodanine-3-acetic acid was introduced as an acceptor/anchor. The molecular structures of D–D–p–A type dyes were characterized using IR, NMR and MS spectral data. The optical, electrochemical, theoretical, light harvesting property, HOMO/LUMO levels, redox behavior, and photovoltaic properties of the synthesized dyes were evaluated. Among the fabricated photovoltaic devices based on the prepared dye, Dpa-Cy dye containing diphenylamine as a donor and cyanoacetic acid as an acceptor exhibited a high-power conversion efficiency of 1.70% with a short-circuit current density (JSC) of 4.48 mA cm?2, an open-circuit photovoltage (VOC) of 0.53 V and a fill factor of 72% under AM1.5 illumination (85 mW cm?2) in comparison with other dyes. Plane-wave calculations indicate that the dye binds reasonably strongly to the TiO2 surface, and the generated DOS picture shows an overlap of the molecular orbitals of the dye and the TiO2 bands. We conclude that the dyes have a promising role as sensitizers in DSSCs.
关键词： rhodanine-3-acetic acid,cyanoacetic acid,carbazole,DSSCs,diphenylamine
更新于2025-09-23 15:21:01
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A novel nematic tri-carbazole as a hole-transport material for solution-processed OLEDs
摘要： Two structural isomers of alkyl-substituted tri-carbazoles were synthesised to study the effect of the substitution pattern on their liquid crystalline behaviour and conductivity and performance in test OLEDs. The isomer with a 2,7-disubstitution pattern in the central carbazole exhibits a monotropic nematic phase, a high conductivity up to 10 Cd A?1 and is suitable as a hole-transport material for solution-processed OLEDs, achieving a high efficiency. The tri-carbazole isomer with a 3,6-substitution pattern, in the central carbazole, does not exhibit observable liquid crystalline behaviour, exhibits conductivity values two orders of magnitude lower than that of its 2,7-disubstituted isomer and performs poorly in OLEDs with the same configuration. Two structural isomers of alkyl-substituted tri-carbazoles A and B exhibit significantly different liquid crystalline behaviour, conductivity and performance in test OLEDs dependent upon their molecular shape.
关键词： nematic mesophases,hole transport materials,Tri-carbazole liquid crystalline isomers,solution-processed OLED
更新于2025-09-23 15:21:01
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New carbazole-based bipolar hosts for efficient green phosphorescent organic light-emitting diodes
摘要： In this work, two new bipolar host materials 3-(5-(9H-carbazol-9-yl)-4’-(1-phenyl-1H-benzo[d]imidazole-2-yl)-[1,1’-biphenyl]-2-yl)-9-phenyl-9H-carbazole (BCZ-PBM) and 3-(5-(9H-carbazol-9-yl)-3’-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1’-biphenyl]-2-yl)-9-phenyl-9H-carbazole (BCZ-TRZ) were designed and synthesized by introducing benzimidazole and triazine groups as acceptor units with carbazole as the donor unit. These two compounds have excellent thermal stability with a high glass transition temperature (Tg > 160°C) and thermal decomposition temperature (Td > 450°C). Green phosphorescent organic light-emitting devices (PHOLEDs) D1 and D2 were obtained by doping Ir(ppy)3 into BCZ-PBM and BCZ-TRZ, in which BCZ-PBM based device D1 revealed better performance with an external quantum efficiency (EQE) of 20.4%, maximum current efficiency (CE) of 69.3 cd/A, and maximum power efficiency (PE) of 54.8 lm/W. Notably, the BCZ-PBM-based device exhibited excellent efficacy stability and a low efficiency roll-off of 1.7% at 1000 cd/m2 and 4.7% at 5000 cd/m2.
关键词： Carbazole,Green PHOLEDs,High efficiency,Bipolar host materials
更新于2025-09-23 15:19:57
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Control of ??a???? stacking in carbazole-benzimidazo???1,2- <i>f</i> ???phenanthridines: the design of electron-transporting bipolar hosts for phosphorescent organic light-emitting diodes
摘要： Two bipolar hosts, 8-cbzBIFP and 10-cbzBIFP, both with basic skeletons of orthogonally-connected carbazole and benzimidazoh1,2-fiphenanthridine (BIFP) have been prepared. The planar structure of the BIFP moiety in comparison to the governs the molecular stacking in the crystal lattice. Electron transport properties, benzimidazole derivatives, are facilitated. Both hosts display fabulous performances in phosphorescent organic light-emitting diodes with bis(2-phenylpyridine)(acetylacetonate)iridium(III) as an emitter. The optimized green PhOLED of 10-cbzBIFP achieves the maximum brightness (Lmax) of 58 810 cd m(cid:2)2, the maximum current e?ciency (Zc) of 87.0 cd A(cid:2)1 and external quantum e?ciency (EQE) of 21.1%. Likewise, 8-cbzBIFP shows an Lmax of 58 870 cd m(cid:2)2, Zc of 77.3 cd A(cid:2)1 and EQE of 19.1%.
关键词： electron-transporting,phosphorescent organic light-emitting diodes,carbazole-benzimidazoh1,2-fiphenanthridines,bipolar hosts,p–p stacking
更新于2025-09-23 15:19:57
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A perspective on blue TADF materials based on carbazole-benzonitrile derivatives for efficient and stable OLEDs
摘要： The advent of materials with thermally activated delayed ?uorescence (TADF) has triggered a wave of research to break the mutual exclusion of high ef?ciency and long lifetime of blue organic light-emitting diodes. Representatively, multiple donor-acceptor-type carbazole-benzonitrile (CzBN) derivatives have realized the longest device lifetimes in the blue region up to now together with high ef?ciencies among all TADF emitters. This perspective timely summarizes the progress of molecular design and device performances of CzBN derivatives and is concluded by providing suggestions on the future development of such materials and the corresponding devices.
关键词： OLEDs,high efficiency,carbazole-benzonitrile derivatives,long lifetime,blue TADF materials
更新于2025-09-23 15:19:57
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Pyridine Bridging Diphenylamine-Carbazole with Linking Topology as Rational Hole Transporter for Perovskite Solar Cells Fabrication
摘要： Developing cost-effective and rational hole transporting materials is critical for fabricating high-performance perovskite solar cells (PSCs) and to promote their commercial endeavor. We have designed and developed pyridine (core) bridging diphenylamine-substituted carbazole (arm) small molecules, named as 2,6PyDANCBZ and 3,5PyDANCBZ. The linking topology of core and arm on their photophysical, thermal, semiconducting and photovoltaic properties were probed systematically. We found that the 2,6PyDANCBZ shows higher mobility and conductivity along with uniform film-forming ability as compared to 3,5PyDANCBZ. The PSCs fabricated with 2,6PyDANCBZ supersede the performance delivered by Spiro-OMeTAD, and importantly also gave improved long-term stability. Our findings put forward small molecules based on core-arm linking topology for cost-effective hole selective layers designing.
关键词： hole transport materials,charge transport,electro-optical properties,perovskite solar cells,Carbazole
更新于2025-09-23 15:19:57
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Stereoregular polymers with pendant carbazolyl groups: Synthesis, properties and optoelectronic applications
摘要： The most recent results concerning the stereospecific synthesis and the microstructural, chemico-physical and optical characterization of polymers containing pendant carbazolyl groups are reviewed for the first time. Stereoregular poly(N-alkenyl-carbazole)s, poly(4-(Ncarbazolyl) methyl styrene), poly(ω-(N-carbazolyl)alkyl acrylate)s and poly(ω-(N-carbazolyl)alkyl metacrylate)s are considered in this review, with a particular focus on the influence of polymer stereochemistry on photophysical behavior. Potential applications of these materials in light-emitting diodes (LEDs), electrochromic devices, electrophotography and holographic memories are also discussed. Among these, we show the appealing results of our experiments, concerning the color tuning in organic LEDs based on poly(N-pentenyl-carbazole) by means of the polymer chain stereoregularity.
关键词： Organic light emitting diode,Carbazole,Optical properties,Stereospecific polymerization
更新于2025-09-23 15:19:57
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Theoretical study on nonlinear optical properties of N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole
摘要： The first-, second- and third-order nonlinear optical properties of N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole in gas phase employing sum-over-states (SOS) method have been calculated for the first time. The ground state molecular structure of N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole was obtained by the geometrical optimizations based on the B3LYP/6-31+G(d) level. The energy of excited states and transition dipole moments between different excited states were obtained by using the time-dependent density functional theory (TDDFT) based on the CAM-B3LYP/Sadlej POL level. Charge transfer during electron excitation was analyzed based on hole and electron distributions. Our calculations showed that the N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole has good nonlinear optical properties and its nonlinear optical properties arise from charge-transfer excitation and local excitation but charge transfer plays the leading role.
关键词： N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole,the time-dependent density functional theory (TDDFT),charge transfer,sum-over-states (SOS) method,nonlinear optical properties
更新于2025-09-19 17:15:36
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Dual nature of exciplexes: exciplex-forming properties of carbazole and fluorene hybrid trimers
摘要： 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-(diphenyl-phosphinyl)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.
关键词： OLEDs,fluorene,exciplexes,hybrid trimers,thermally activated delayed fluorescence,carbazole
更新于2025-09-19 17:15:36