Two structural isomers of carbazole decorated with triarylamine have been designed and synthesized with a facile synthetic procedure. The impact of triarylamine substitution on the isomeric structural linkage of carbazole on the optical, thermal, electrochemical, and photovoltaic properties has been extensively studied by combining experimental and simulation methods. Car­[2,3] showed a red shift in the absorption maximum compared to that of Car­[1,3], indicating the linear conjugation along the 2,7-position of carbazole in the former. The high thermal decomposition temperature (>420 °C) of these compounds could be attributed to the rigid structure of the carbazole core. Perovskite solar cells fabricated with Car­[2,3] as the hole transporting material (HTM) displayed the highest power conversion efficiency (PCE) of 19.23%. It can be attributed to the suitable energy alignment of the highest occupied molecular orbital (HOMO) of HTM with the adjacent perovskite valence band energy level, which results in efficient hole transport. Furthermore, the molecular dynamic simulation demonstrates that the triphenylamine substitution on the 2,3,6,7 positions of Car­[2,3] results in a more planar molecular alignment on top of the perovskite surface, promoting an efficient hole extraction. Essentially, when Car­[1,3] and Car­[2,3] were applied in perovskite solar cells, they showed enhanced long-term stability by retaining >80% of their initial PCEs after 1000 h of continuous illumination.

alternative to the existing conventional energy sources. [1] Organometal-halide perovskites show exceptional panchromatic light harvesting ability, high molar extinction coefficient, high charge carrier mobilities, and long electron-hole diffusion lengths. Further, the versatility and tunable electronic properties of perovskites are beneficial for realizing higher photovoltaic performance reaching over 25%. [2][3][4][5] However, low charge extraction and poor stability of the metal-halide perovskite limit their credentials in large-scale applications.To overcome these limitations, p-type semiconducting materials, also known as hole-transporting materials (HTMs), were sandwiched between perovskite and metal electrode. HTMs play a vital role in PSCs to extract and transfer the positive charges and thus achieve high efficiency. [6][7][8][9][10] They can be classified as inorganic, [11] polymeric, [12] and small molecular organic HTMs. [13,14] Among them, small molecular HTMs are superior to other counterparts owing to their structural diversity, well-defined molecular Triarylamine-substituted bithiophene (BT-4D), terthiophene (TT-4D), and quarterthiophene (QT-4D) small molecules are synthesized and used as low-cost hole-transporting materials (HTMs) for perovskite solar cells (PSCs). The optoelectronic, electrochemical, and thermal properties of the compounds are investigated systematically. The BT-4D, TT-4D, and QT-4D compounds exhibit thermal decomposition temperature over 400 °C. The n-i-p configured perovskite solar cells (PSCs) fabricated with BT-4D as HTM show the maximum power conversion efficiency (PCE) of 19.34% owing to its better hole-extracting properties and film formation compared to TT-4D and QT-4D, which exhibit PCE of 17% and 16%, respectively. Importantly, PSCs using BT-4D demonstrate exceptional stability by retaining 98% of its initial PCE after 1186 h of continuous 1 sun illumination. The remarkable long-term stability and facile synthetic procedure of BT-4D show a great promise for efficient, stable, and low-cost HTMs for PSCs for commercial applications.

Highly efficient deep-blue emission is crucial to realize energy-efficient and high-quality display and solid-state lighting applications. A solution-processable deep-blue emitter is essential for producing cost-effective large-area devices via roll-to-roll fabrication. Here, we demonstrate a highly efficient solution-processable deep-blue organic light-emitting diode by utilizing a carbazole-based fluorescent emitter 6-((9,9-dibutyl-7-((7-cyano-9-(2-ethylhexyl)-9H-carbazol-2-yl)­ethynyl)-9H-fluoren-2-yl)­ethynyl)-9-(2-ethylhexyl)-9H-carbazole-2-carbonitrile (JV55). The resultant device showed a maximum external quantum efficiency (EQE) of 6.5% and an EQE of 5.5% at 100 cd/m2 with CIE coordinates of (0.16, 0.06). The optimized device showed a maximum EQE of 6.5%. Additionally, the deep-blue emission also realized a 101% color saturation according to the NTSC standard. The high efficiency may be attributed to engineering appropriate device architecture and enabling balanced carrier injection, effective host-to-guest energy transfer, the emissive layer having a very high quantum yield of 91%, utilizing a host with high triplet energy so as to confine exciton on the guest, and low doping concentration inhibiting efficiency roll-off due to concentration quenching.

New organic materials containing a cyano‐functionalized carbazole moiety at one end linked to different chromophores such as fluorene, carbazole, and triphenylamine at the other end through an acetylene spacer are synthesized and characterized by photophysical, electrochemical, thermal, and electroluminescence studies. A meta‐like linkage at the C‐2 and C‐7 atoms of the central carbazole moiety and the choice of chromophore restricted the emission to the near‐ultraviolet region. The photophysical properties of the compounds depend on the nature of the chromophore attached to the carbazole unit. A triphenylamine‐substituted derivative exhibited the longest wavelength emission in the series, attributable to the elongated conjugation and electron richness of triphenylamine, whereas the phenyl‐ and fluorene‐functionalized molecules showed the shortest wavelength emissions with vibronic patterns. The compounds containing carbazole and triphenylamine units exhibited positive solvatochromism in their fluorescence spectra, and this behavior is characteristic of charge transfer from a donor to an acceptor. A fluorene derivative containing cyano substituents at the carbazole and fluorene moieties exhibited the best electroluminescence characteristics in the series, probably because of balanced charge transport and effective confinement of the excitons in the emissive layer.

Two tetrathioalkyl-substituted bithiophene-based small molecule quinoids (TSBTQs) having different chain lengths (thio– hexyl and –decyl) are synthesized and applied as an n-type active component in organic field effect transistors (OFETs)....

A series of carbazole-based dyes functionalized with different auxochromes via vinyl linker have been synthesized and characterized. A progressive shift in the absorption maximum is observed as the conjugation and electron-donating nature of chromophore increases. Dyes containing electron-releasing terminal groups such as triphenylamine and carbazole exhibited positive emission solvatochromism attributable to an induced intramolecular charge transfer from triphenylamine/carbazole donor to cyano acceptor. The superior electroluminescence performance of disubstituted dyes demonstrates the role of an additional cyanocarbazole in achieving balanced charge transport compared to monosubstituted analogues. In addition, the electroluminescence performance of the dyes exhibited trends attributable to the electron richness of the linker/terminal chromophore. Thus, the carbazole-based derivatives displayed better electroluminescence efficiency than the analogous fluorene derivatives. Similarly, 2,7-substituted carbazole derivative exhibited better performance than the 3,6-substituted carbazole derivative. A doped electroluminescent device containing 3 wt % tricarbazole derivative showed blue emission with a high external quantum efficiency of 5.3% at a practical brightness of 1000 cd/m 2 .

High efficiency deep-blue emission is essential to realize energy-saving, high-quality display and lighting applications. We demonstrate here a deep-blue organic light emitting diode using a novel carbazole based fluorescent emitter 7-[4-(diphenylamino)phenyl]-9-(2-ethylhexyl)-9Hcarbazole-2-carbonitrile (JV234). The solution processed resultant device shows a maximum luminance above 1,750 cd m %2 and CIE coordinates ð0:15; 0:06Þ with a 1.3 lm W %1 power efficiency, 2.0 cd A %1 current efficiency, and 4.1% external quantum efficiency at 100 cd m %2 . The resulting deep-blue emission enables a greater than 100% color saturation. The high efficiency may be attributed to the effective host-to-guest energy transfer, suitable device architecture facilitating balanced carrier injection and low doping concentration preventing efficiency roll-off caused by concentration quenching.

Triarylamine end-capped-functionalized arylene-imidazole derivatives were synthesized from readily accessible, inexpensive precursors and employed as hole transporting materials (HTMs) in perovskite solar cells (PSCs). All the HTMs displayed high thermal decomposition temperatures (>410 °C), which is beneficial for realizing stable PSC devices. In addition, the new HTMs show appropriate energy level alignment with the perovskite layer, ensuring efficient hole transfer from perovskites to HTMs. Interestingly, PSCs fabricated with the triarylamine-functionalized imidazolyl-capped bithiophene molecule (DImBT-4D) as the HTM exhibited the best power conversion efficiency of 20.11%, comparable to that of the benchmark HTM spiro-OMeTAD, prompting it be a prospective candidate for large-scale PSC applications.