Efficient blue-emitting electrophosphorescent organic light-emitting diodes using 2-(3,5-di(carbazol-9-yl)phenyl)-5-phenyl-1,3,4-oxadiazole as an ambipolar host
作者:Yadong Zhang、Wojciech Haske、Dengke Cai、Stephen Barlow、Bernard Kippelen、Seth R. Marder
DOI:10.1039/c3ra43720e
日期:——
2-(3,5-Di(carbazol-9-yl)phenyl)-5-phenyl-1,3,4-oxadiazole, 1, was synthesised from the reaction of 3,5-di(carbazol-9-yl)benzohydrazide and trimethyl orthobenzoate at 185 °C. Compound 1 exhibits a glass-transition temperature of 120 °C, a reversible reduction at a half-wave potential of −2.34 V vs. ferrocenium/ferrocene, and an adiabatic triplet energy of 2.73 eV. Organic light-emitting diodes were fabricated using: solution-processed poly[6-(9H-carbazol-9-yl)-9-(4-vinylbenzyl)-9H-3,9′-bicarbazole] as the hole-transport layer; a vacuum-deposited emissive layer composed of 1 as a host and bis[(4,6-di-fluorophenyl)pyridinato-N,C2′](picolinato-N,O)iridium or fac-tris(2-phenylpyridinato-N,C2′)iridium as blue- or green-emitting phosphorescent guest molecules, respectively; and vacuum-deposited 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline or 3-([1,1′-biphenyl]-4-yl)-5-(4-(tert-butyl)phenyl)-4-phenyl-4H-1,2,4-triazole as the electron-transport layer. External quantum efficiencies of up to 21 and 25% were obtained for blue- and green-emitting devices, respectively.
2-(3,5-Di(carbazol-9-yl)phenyl)-5-phenyl-1,3,4-oxadiazole, 1 是由 3,5-di(carbazol-9-yl)benzohydrazide 和原苯甲酸三甲酯在 185 °C 下反应合成的。化合物 1 的玻璃跃迁温度为 120 ℃,对二茂铁/二茂铁的半波电位为 -2.34 V,可逆还原,绝热三重能为 2.73 eV。有机发光二极管是利用溶液加工聚[6-(9H-咔唑-9-基)-9-(4-乙烯基苄基)-9H-3,9′-二咔唑]作为空穴传输层;真空沉积的发射层,由 1 作为主分子,双[(4,6-二氟苯基)吡啶-N,C2′](吡啶-N,O)铱或三(2-苯基吡啶-N,C2′)铱分别作为蓝色或绿色发射磷光客体分子组成;以及真空沉积的 2,9-二甲基-4,7-二苯基-1,10-菲罗啉或 3-([1,1′-联苯]-4-基)-5-(4-(叔丁基)苯基)-4-苯基-4H-1,2,4-三唑作为电子传输层。蓝色和绿色发光器件的外部量子效率分别高达 21% 和 25%。