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Carbazole‐derived self‐assembled monolayers (SAMs) with excellent hole‐extraction and injection properties are promising hole‐transporting materials for perovskite optoelectronic devices, including perovskite solar cells (PSCs) and perovskite light‐emitting diodes (PeLEDs). The performance and thermal stability of these SAMs are heavily influenced by their chemical structure. Herein, the construction of fused carbazole‐based SAMs is proposed by expanding the π‐conjugation of the carbazole unit for application in PSCs and PeLEDs. Three proof‐of‐concept SAMs are designed and synthesized, termed XS8, XS9, and XS10, that feature highly rigid and planar fused carbazole as the donor and a conjugated alkene unit as the linker. This conjugated extension improves planarity, stability, and enhances the molecular dipole moment. Among these, XS10, with the highest degree of conjugation, demonstrated superior performance in perovskite‐based devices. The PSC device utilizing XS10 achieves a maximum power conversion efficiency (PCE) of 20.28%, surpassing the 17.19% PCE of the classic 2PACz‐based device. Similarly, the PeLED device with XS10 achieves a maximum external quantum efficiency (EQE) of 16.6%, compared to 14.5% for PEDOT‐based devices. This work provides a novel molecular design strategy for creating efficient and stable SAMs for perovskite optoelectronics and other organic electronic devices. [ABSTRACT FROM AUTHOR]

Herein, two new spiro-cored hole-transporting materials (HTMs), termed HT1 and HT2, are designed and synthesized, breaking the symmetry of the classical HTM, spiro-OMeTAD, by introducing benzo[d]imidazole with diverse electron characteristics of two nitrogen atoms to improve their hole-transporting properties. Both HT1 and HT2 exhibited excellent thermal stability with glass transition temperatures (Tg) of 162 and 197 °C, respectively, and good hole transport capability with hole mobilities of 8.26 × 10−5 and 1.08 × 10−4 cm2 V−1 s−1, respectively. When utilized in green perovskite quantum dot light-emitting diodes (Pe-QLEDs), the devices achieved low turn-on voltages of 3.0 and 2.8 V, maximum external quantum efficiency (EQEmax) of 7.6 and 6.7% and high maximum luminance of 45 056 and 46 382 cd m−2, respectively. The excellent hole-transporting properties and great device performance show that HT1 and HT2 are promising HTMs for Pe-QLEDs. [ABSTRACT FROM AUTHOR]

Full colour display is vital to organic lighting-emitting diodes (OLEDs) and universal hosts for all red, green and blue (RGB) OLEDs are strongly desired. In this work, a universal bipolar host, namely BCz3PhCN, was synthesized by simply incorporating carbazole and isonicotinonitrile units. BCz3PhCN exhibits excellent thermal stability and a high triplet energy level (ET) of 2.76 eV; therefore, all RGB devices were fabricated to evaluate their electroluminescent (EL) performance. The blue device hosted by BCz3PhCN was lit at 3.0 V with the maximum external quantum efficiency (EQEmax) of 16.22%. Green PhOLEDs exhibited a better performance with the maximum luminance (Lmax) of 1 21 900 cd m−2, maximum current efficiency (ηc,max) of 69.30 cd A−1, maximum power efficiency (ηp,max) of 64.88 lm W−1 and EQEmax of 20.04%. Remarkably, the highest EQEmax of 26.84% was achieved by the red device in the low luminance range. The above excellent EL performance for all BCz3PhCN-based blue, green and red devices indicates a huge potential for BCz3PhCN as a universal host in developing high-performance monochrome and white OLEDs. [ABSTRACT FROM AUTHOR]

In this paper, two new bipolar host materials 7-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)benzo[5,6][1,4]dioxino[2,3-b]pyrazine (HF1) and 7-(4′-(9H-carbazol-9-yl)-[1,1′-biphenyl]-4-yl)benzo[5,6][1,4]dioxino[2,3-b]pyrazine (HF2) are reported through introducing dioxino[2,3-b]pyrazine as the acceptor unit and carbazole as the donor unit. The two compounds exhibit excellent thermal stability and morphological stability, and have appropriate frontier orbital energy levels. Employing HF1 and HF2 as the host, the fabricated Ir(pq)2acac-based devices exhibit intrinsic red emission at 600 nm, and the maximum brightness/maximum external quantum efficiency (EQE) reaches 49 760 cd m−2/15.1% and 57 990 cd m−2/12.8% for HF1- and HF2-hosted devices, respectively. These results show that HF1 and HF2 have huge potential in organic light-emitting diode (OLED) applications. [ABSTRACT FROM AUTHOR]

Abstract In this work, two host materials, 9-(4-(7-(9,9'-spirobi[fluoren]−2-yl)-[1,2,4]triazolo[1,5- a ]pyridin-2-yl)phenyl)−9H-carbazole (CzTPSp1) and 9-(4-(6-(9,9'-spirobi[fluoren]−2-yl)-[1,2,4]triazolo[1,5- a ]pyridin-2-yl)phenyl)−9H-carbazole (CzTPSp2) were designed and synthesized by utilizing carbazole as hole-transport units and [1,2,4]triazolo[1,5- a ]pyridine (TP) as electron-transport units. These two compounds exhibit good thermal stability, appropriate frontier orbital energy levels, high triplet energy levels, and balanced carrier transport properties. Red phosphorescent organic light-emitting devices (PhOLEDs) based on these two hosts and bis(1-phenylquinoline) (acetylacetonate)iridium (III) (Ir(pq) 2 acac) exhibit satisfactory efficiencies with the maximum external quantum efficiency (η ext, max) of 23.0% and 22.1%. To our knowledge, among the red-emitting OLEDs based on Ir(pq) 2 acac, the η ext, max (23.0%) of our device is the highest reported so far. Meanwhile, efficiency roll-off in these devices are far less obvious, at the luminance of 1000 cd m−2, the η ext of devices R1 and R2 can reach to be 22.0% and 21.6% with the efficiency roll-off value of 4.3% and 2.2%. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Three bipolar hosts, 9-(4-(2,3-diphenylquinoxalin-6-yl)phenyl)-9 H -carbazole ( p -PQPC ), 9-(3-(2,3-diphenylquinoxalin-6-yl)phenyl)-9 H -carbazole ( m -PQPC ) and 9-(2-(2,3-diphenylquinoxalin-6-yl)phenyl)-9 H -carbazole ( o -PQPC ) were designed, synthesized and characterized for red phosphorescence organic light emitting devices (PhOLEDs). These three compounds exhibited excellent physical properties with high thermal stabilities, reasonable HOMO-LUMO energy levels and balanced charge transport. All of them were applied to fabricate red PhOLEDs as host materials, and the p -PQPC based device demonstrated outstanding electroluminescence performance with the maximum current efficiency, power efficiency and external quantum efficiency of 21.9 cd/A, 15.4 lm/W and 12.2%, respectively, which suggesting that p -PQPC is a promising host for red PhOLEDs. [ABSTRACT FROM AUTHOR]

Two novel D-A-D-A-D type molecules T1 and T2 based on substituted dihydroindolo [3, 2-b] carbazole with large two-photon absorption (2PA) cross section and excellent aggregation-induced enhanced emission (AIEE) property have been synthesized and characterized. Both compounds emit weakly fluorescent in THF, while a significant AIEE property is observed in water/THF (v/v 50%/50%) for T1 and water/THF (v/v 90%/10%) for T2 with a sharp increase in fluorescence intensity. The solid fluorescence of T1 and T2 is located at 575 nm and 588 nm, and their quantum efficiencies are determined to be 3.2% and 5.8%, respectively. The corresponding 2PA cross section values for T1 and T2 at 800 nm are 867 GM and 1300 GM by the open-aperture Z-scan technique. These excellent performances of both compounds make them as attractive alternatives for biophotonic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Two novel indole-based, bipolar, host materials were designed and synthesized by introducing the triazine unit to the 5-position of indole moiety with a meta -linking strategy. The two host materials exhibited excellence bipolar transport abilities and the meta-linking analog presented a high T g value (>120 °C). Furthermore, their electrochemical and photo-physical properties were also fully characterized and all the results exhibited that the meta -linking strategy made a significant effect on the physical properties of the two hosts. Moreover, the PHOLED devices using 9-(4-(5-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)- 1H -indol-1-yl) phenyl)- 9H -carbazole and 9-(4-(5-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)- 1H -indol-1-yl)phenyl)- 9H -carbazole as hosts were also fabricated to evaluate the practical utilities of host materials. The devices achieved the maximum external quantum efficiencies of 17.53% for para -linking compound and 14.53% for meta -linking analog, respectively. In particular, para -linking compound based device revealed the maximum external quantum efficiency was twice that of the device using 4,4′-bis( N -carbazolyl)-1,10-biphenyl as the host. [ABSTRACT FROM AUTHOR]

In this paper, two new bipolar host materials (CZ- p -TRZ and CZ- m -TRZ) which consist of 9-phenylcarbazole as the donor and 2,4,6-triphenyl-1,3,5-triazine as the acceptor were synthesized and characterized. Two compounds exhibit excellent thermal stability and appropriate triplet energy levels (E T). Based on the above advantages, Ir(ppy) 3 -based green phosphorescent organic light-emitting diodes (PhOLEDs) were fabricated with CZ- p -TRZ and CZ- m -TRZ as host. Both PhOLEDs show good performance with maximum external quantum efficiencies (EQE max) of 16.83 and 19.40%, respectively. Especially, two devices also exhibit extremely small efficiency roll-off, and at a practical luminance of 1000 cd/m2, only 0.1% drop in efficiency was observed for two devices, which is among the best results ever reported as green bipolar hosts. [Display omitted] • Two bipolar hosts based on carbazole and triazine are presented. • The materials show excellent thermal stability and appropriate HOMO/LUMO levels. • Green devices hosted by CZ- p -TRZ and CZ- m -TRZ exhibit extremely low efficiency roll-offs with 0.1% decrease at 1000 cd/m2. [ABSTRACT FROM AUTHOR]

In this work, three bipolar host materials combined electron-rich carbazole moiety and electron-deficient benzonitrile and benzo[ d ]imidazole units were firstly designed and synthesized, namely 3''-(9 H -carbazol-9-yl)-5'-(1-phenyl-1 H -benzo[ d ]imidazole-2-yl)-[1,1':3′,1″-terphenyl]-4-carbonitrile ( p -PNBMCz), 3''-(9 H -carbazol-9-yl)-5'-(1-phenyl-1 H -benzo[ d ]imidazole-2-yl)-[1,1':3′,1″-terphenyl]-3-carbonitrle ( m -PNBMCz) and 3''-(9 H -carbazol-9-yl)-5'-(1-phenyl-1 H -benzo[ d ]imidazole-2-yl)-[1,1':3′,1″-terphenyl]-2-carbonitrle ( o -PNBMCz), respectively. The glass transition temperatures (T g) of all the materials are above 117 °C, demonstrating a good morphological stability, and the thermal decomposition temperatures (T d) are over 436 °C, reflecting remarkable thermal properties. Besides, their HOMO separated fully with LUMO, which is conducive to both hole and electron transporting. They also possess a triplet energy level (E T) of about 2.7 eV, which qualifies them to be hosts for green and red phosphorescent emitters. Green phosphorescent organic light-emitting diodes (PhOLEDs) hosted by these three materials were manufactured and they displayed good performance with very low turn-on voltages (V on). Remarkably, the device hosted by p -PNBMCz (G1) exhibits maximal external quantum efficiencies (EQE) of 17.1% and maximal power efficiency (η p,max) of 69.2 lm/W with a minor efficiency roll-off, the η ext still remains to be 15.9% with only a 7% roll-off percentage as the luminance reaches 1000 cd/m2. [Display omitted] • Three novel bipolar hosts p / m / o -PNBMCz based on carbazole, benzonitrile and benzo[ d ]imidazole were designed and synthesized. • All these materials exhibited excellent thermal stability (T g > 117 °C, T d > 436 °C) and full separation of HOMO/LUMO levels. • Device G1 hosted by p -PNBMCz exhibited the best EL performance with a low V on (2.4 V) and a high η p,max (69.2 lm/W). [ABSTRACT FROM AUTHOR]

In this work, by introducing triphenylvinyl group to the backbone of N , N -diaryl fluorenamine, three novel hole transport materials (HTMs), namely TFlA-BP , TFlA-Fl and TFlA-Nap , were designed and synthesized. These materials exhibit excellent thermal stability, high triplet energy levels (E T), appropriate highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels. Double layer green OLEDs with TFlA-BP , TFlA-Fl and TFlA-Nap as hole transport layer (HTL) show good electroluminescence (EL) performance with the maximum power efficiencies (η p) and external quantum efficiency (EQE) of 3.40 lm W−1/1.29%, 3.12 lm W−1/1.35% and 3.15 lm W−1/1.29%, respectively, which are comparable to that of the NPB-based one (2.63 lm W−1/1.36%). [Display omitted] • Three novel HTMs based on triphenylvinyl substituted N , N -diaryl fluorenamine were presented. • All the materials exhibited excellent thermal stability, appropriate HOMO/LUMO and E T levels. • Devices employing them as HTL exhibited comparable EL performances compared to that of the NPB-based one. [ABSTRACT FROM AUTHOR]

In this research, a novel macrocycle containing tetrabenzeneaza has been developed as a novel building block for hole transport materials (HTMs). Benefiting from its unique highly twisted spatial configuration, this macrocycle exhibits high triplet energy level (E T) as well as high hole mobility. Based on this aza macrocycle, two hole transporting materials, namely 2TPATPCA and 2CzTPCA , were designed and synthesized. Both 2TPATPCA and 2CzTPCA possess enough E Ts, appropriate frontier orbital energy levels as well as good thermal stability, which promote them as universal HTMs in multicolor phosphorescent organic light-emitting devices (PhOLEDs) and thermal activated delay fluorescence (TADF) OLEDs. High external quantum efficiencies (EQEs) were realized in OLEDs using the these two HTMs. For example, sky bule PhOLED with 2CzTPCA showed a significantly improved maximum EQE of 20.3% compared to that of the reference device using N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) (EQE of 14.2%) and 4,4′-Cyclohexylidenebis[N,N- bis(4-methyl phenyl)aniline (TAPC) (EQE of 12.2%). Green TADF OLED using 2CzTPCA as HTM also exhibit a much improved maximum EQE of 17.9% compared to that of the reference device based on NPB (EQE of 10.3%). These results indicate this tetrabenzeneaza macrocyclic is a promising building block for developing universal high-performance HTMs. Image 1 • Developed a novel platform – tetrabenzenacyclohexaphane for building HTMs. • Tetrabenzenacyclohexaphane derivatives exhibited high triplet energies, good thermal stability, and high hole-transporting abilities. • Universal HTMs based on tetrabenzenacyclohexaphane in multicolor PhOLEDs and TADF OLEDs exhibited superior performance. [ABSTRACT FROM AUTHOR]

In this work, two new bipolar host materials 3-(5-(9 H -carbazol-9-yl)-4'-(1-phenyl-1 H -benzo d imidazole-2-yl)-[1,1′-biphenyl]-2-yl)-9- phenyl-9 H -carbazole (BCZ-PBM) and 3-(5-(9 H -carbazol-9-yl)-3'-(4,6- diphenyl-1,3,5-triazin-2-yl)-[1,1′-biphenyl]-2-yl)-9-phenyl-9 H -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 (T g > 160 °C) and thermal decomposition temperature (T d > 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. Image 1 • Two new bipolar host materials were synthesized by introducing benzimidazole, triazine and carbazole groups. • The compounds showed excellent thermal stability with the high T g and T d. • Maximum EQE of 20.4%, CE of 69.3 cd/A, and PE of 54.8 lm/W of green PHOLED based on DCZ-PBM was demonstrated. [ABSTRACT FROM AUTHOR]

Two host heterocyclic compounds 5-(dibenzo[b,d]furan-4-yl)-1-(4,6-diphenyl-1,3,5-triazin-2-yl)-1H-indole (FITRZ) and 5-(dibenzo[b,d]thiophen-4-yl)-1-(4,6-diphenyl-1,3,5-triazin-2-yl)-1H-indole (TITRZ) were synthesized by C N coupling reaction of triazine and dibenzothiophene/dibenzofuran moiety with a 1,5-bridged indole unit. Their photo-physical, thermal and electrochemical properties were fully explored, and the results indicate that both of them are promising phosphorescent host materials for green and red PhOLED devices with low on-set potentials. For example, the green PHOLED based on TITRZ showed the maximum current and external quantum efficiency up to 85.9 cd/A and 23.7%. Meanwhile, the red PhOLED based on FITRZ yielded the maximum current and external quantum efficiency of 41.3 cd/A and 18.8% with a turn-on voltage of 3.0 V. Image 1 • Noble host materials for green and red PhOLED devices with low on-set potentials. • Green PHOLED based on TITRZ with EQE up to 23.7%. • Red PhOLED based on FITRZ yielded EQE of 18.8% with a turn-on voltage of 3.0 V. [ABSTRACT FROM AUTHOR]

In this work, seven small molecular compounds named N,N -diphenyl-4-(2-phenylpyrimido [1,2-b]indazol-4-yl)aniline (1) , N , N -diphenyl-4-(5-phenylpyrazolo [1,5- a pyrimidin-7-yl)aniline (2) , N , N -diphenyl-4-(5-phenyl- [1,2,4]triazolo [1,5- a pyrimidin-7-yl)aniline (3) , 4,4'-(pyrimido [1,2-b]indazole-2,4-diyl)bis (N,N -diphenylaniline) (4) , 4,4'-(pyrazolo [1,5- a pyrimidine-5,7-diyl)bis (N , N -diphenylaniline) (5) , 4,4'-([1,2,4]triazolo [1,5- a pyrimidine-5,7-diyl)bis (N , N -diphenylaniline) (6) , N , N -diphenyl-4-(4-phenylpyrimido [1,2-b]indazol-2-yl)aniline (7) with donor-acceptor (D-A) structure were designed and synthesized by employing triphenylamine (TPA) as donor and indazole, pyrazole and/or triazole as acceptor. Systematic study and analysis on thermal, photophysical, electrochemical properties of all compounds were performed. All compounds exhibit good thermal and morphological stabilities with decomposition temperatures (T d) range from 270 to 462 °C, and glass transition temperatures (T g) range from 78 to 127 °C. The investigation of photophysical properties of these compounds revealed that all these compounds are of high photoluminescence quantum yields (PLQY), particularly for compound 6 , whose PLQY value was as high as 90.22%. To explore potential applications of these materials in organic light-emitting diodes (OLEDs), two devices with compounds 2 and 5 were fabricated. Both devices show excellent device performances with maximum current efficiency, maximum power efficiency and external quantum efficiency of 15.9 cd A−1, 10.4 l m W-1 and 8.4% for compound 2- based device and 10.1 cd A−1, 5.8 l m W-1 and 5.5% for compound 5- based device, respectively. Image 1 • Seven D-A type EL materials with the hole-transporting unit TPA and three different azole electron-transporting units were synthesized • These bipolar host materials exhibited good thermal and morphological stabilities, as well as high photoluminescence quantum yields. • Two materials were selected for fabrication of red fluorescent OLED devices and exhibited excellent device performance. [ABSTRACT FROM AUTHOR]

In this paper, three novel bipolar host materials, 9,9′-Diphenyl-6-(4-pyridinyl)-3,3′-bicarbazole(BCz4Py), 9,9′-Diphenyl-6-(3-pyridinyl)-3,3′-bicarbazole(BCz3Py) and 9,9′-Diphenyl-6-(5-pyrimidinyl)-3,3′-bicarbazole(BCz5Pm), were synthesized by incorporation of bicarbazole as donor with pyridine/pyridimide based N-hexahydroxy nitric heterocycle as acceptor units. The photophysical, thermal and electrochemical properties of these three materials were fully investigated. These compounds all exhibited superior thermal stability with high glass-transition temperature (T g > 130 °C) and decomposition temperature (T d > 400 °C). Appropriate HOMO (highest occupied molecular orbitial) -LUMO (lowest unoccupied molecular orbital) levels and triplet energy (2.74–2.75 eV) of these compounds make them suitable hosts for green iridium pohosphor Ir(ppy) 3 in phosphorescent organic light emitting devices (PhOLEDs). Among them, the BCz3Py hosted device exhibited outstanding performance with maximum external quantum efficiency (EQE) of 14.9%, maximum current efficiency (CE) of 49.9 cd/A, and maximum power efficiency (PE) of 29.1 lm/W, suggesting that BCz3Py is a promising bipolar material for high-efficiency green PhOLEDs. Image 1 • Three novel bipolar host materials were synthesized by incorporation of bicarbazole as donor with pyridine/pyridimide based N-hexahydroxy nitric heterocycle as acceptor units. • The synthesis and characterization of these three compounds have been carried out thoroughly. • The green OLEDs based on three compounds were systematically compared. • The performance of the device based on BCz3Py is impressive with a max EQE of 14.9%. [ABSTRACT FROM AUTHOR]