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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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Regioisomer effects of dibenzofuran-based bipolar host materials on yellow phosphorescent OLED device performance
摘要： Four regioisomers were synthesized for use as bipolar host materials for phosphorescent organic light-emitting diodes (PhOLEDs) by classic cross-coupling reactions using cyanofluorene and fused dibenzofuran and were readily purified. To realize the bipolar host material, a cyano-substituted fluorene was selected as the n-type unit and dibenzofuran as the p-type unit. Yellow PhOLEDs were fabricated with iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C20)acetylacetonate [PO-01] as a phosphorescent emitter. The achieved maximum current efficiency was 77.2 cd A?1 and the external quantum efficiency was 25.3% for the [PO-01]-based PhOLED; the 7-(dibenzo[b,d]furan-2-yl)-9,9-dimethyl-9H-fluorene-2-carbonitrile (CF-2-BzF) host had the best device performance. The color coordinates of yellow PhOLEDs at 1000 cd m?2 were (0.50, 0.50) (CF-1-BzF), (0.50, 0.49) (CF-2-BzF), (0.51, 0.49) (CF-3-BzF), and (0.50, 0.50) (CF-4-BzF).
关键词： regioisomer effects,phosphorescent organic light-emitting diodes,device performance,bipolar host materials,yellow PhOLEDs
更新于2025-09-23 15:19:57
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Diphenylamine/triazine hybrids as bipolar hosts for phosphorescent organic light-emitting diodes
摘要： The bipolar host materials employing diphenylamine (DPA) as donor unit and triazine (TRZ) as acceptor unit could achieve suitable energy levels and balanced charge transporting properties, which are necessary for high performance of organic light-emitting diodes (OLEDs). In this work, three DPA/TRZ based host materials, named 2-(4-(N,N-diphenylamino)phenyl)-4,6-diphenyl-1,3,5-triazine (DPA-TRZ), 2,4-bis(4-(N,N-diphenylamino)phenyl)-6-phenyl-1,3,5-triazine (DDPA-TRZ), and 2,4,6-tris(4-(N,N-diphenylamino)phenyl)-1,3,5-triazine (TDPA-TRZ) were designed and synthesized. Their thermal, photophysical, electrochemical, and carrier transporting properties were investigated to reveal the relationship between molecular structure and properties. The number of DPA units could regularly tune the optical and electrical properties of the hybrids. The triplet excited state energy (ET) values of DPA-TRZ, DDPA-TRZ, and TDPA-TRZ are 2.38, 2.51, and 2.73 eV, respectively. To evaluate the electroluminescent properties of the three host materials, blue, green, red, and white phosphorescent OLEDs (PhOLEDs) were fabricated and characterized. With the highest ET value, TDPA-TRZ can afford from blue to red phosphorescent emitters. All these devices exhibited EQEs of over 20% with relatively low efficiency roll-offs. The single-host white PhOLEDs based on TDPA-TRZ showed impressive color stability and superior color rendition. These results demonstrate that the combination of DPA and TRZ is an effective way to construct highly efficient bipolar host materials.
关键词： diphenylamine,triazine,phosphorescent organic light-emitting diodes,charge transporting properties,bipolar host materials
更新于2025-09-23 15:19:57
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Chromenopyrazole-based bipolar host materials for solution-processable thermally activated delayed fluorescence OLEDs exhibiting high efficiency and low roll-off
摘要： This study reports the design, synthesis, and characterization of two new bipolar host materials, DCzCP and TCzCP. Both materials were implemented as hosts by doping a known green thermally activated delayed fluorescent (TADF) emitter (t4CzIPN) in solution-processable OLEDs. DCzCP-based devices a?ord the best performance with the maximum external quantum e?ciency (EQE) of 21.2%. Notably, the EQE was maintained at 20.7% and 19.7% at a practical luminance of 500 cd m(cid:2)2 and 1000 cd m(cid:2)2, respectively, demonstrating very small roll-o?.
关键词： thermally activated delayed fluorescence,high e?ciency,bipolar host materials,low roll-o?,Chromenopyrazole,OLEDs,solution-processable
更新于2025-09-16 10:30:52
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Oxadiazole derivatives as bipolar host materials for high-performance blue and green phosphorescent organic light-emitting diodes
摘要： By combining two n-type groups, pyridine and oxadiazole, with one p-type carbazole group, two novel bipolar hosts, namely 2-(3-(9H-carbazol-9-yl)-[1,10-biphenyl]-3-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (PyOxd-mCz) and 2-(40-(9H-carbazol-9-yl)-[1,10-biphenyl]-3-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (PyOxd-pCz) have been developed as hosts for blue and green phosphorescent organic light-emitting diodes (PhOLEDs). The two compounds exhibit similar HOMO levels of ?5.64 eV for PyOxd-mCz and ?5.63 eV for PyOxd-pCz and the same LUMO level of ?2.60 eV. With a more twisted configuration due to meta connections, PyOxd-mCz possesses a higher triplet energy level (ET = 2.77 eV) and more balanced carrier transport than PyOxd-pCz (ET = 2.60 eV). PyOxd-mCz hosted devices achieve a peak current efficiency of 39.7 cd A?1 and a maximum EQE of 20.8% with a low turn-on voltage of 3.5 V for FIrpic and 55.2 cd A?1 and 16.4% for Ir(ppy)3. Apart from the appropriate frontier molecular orbital levels and sufficiently high triplet energy of PyOxd-mCz, the more balanced carrier transport plays a key role for excellent device performance.
关键词： phosphorescent organic light-emitting diodes,bipolar host materials,blue and green PhOLEDs,PyOxd-mCz,PyOxd-pCz
更新于2025-09-16 10:30:52