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Indexed by:期刊论文

Date of Publication:2013-01-28

Journal:JOURNAL OF MATERIALS CHEMISTRY C

Included Journals:SCIE、EI、Scopus

Volume:1

Issue:4

Page Number:757-764

ISSN No.:2050-7526

Abstract:N,N ?Dicarbazolyl-4,4 ?biphenyl (CBP) is one of the most successful uni-polar host materials for phosphorescent organic light-emitting diodes (PhOLEDs). We report the synthesis and properties of one novel CBP derivative, CBP-CN, with two cyano groups (CN) at the 3-site of carbazole rings. The strong electron-withdrawing CN group was introduced with the expectation to promote electron-injecting/-transporting abilities and to achieve bipolar features for CBP-CN. In comparison with the parent CBP, CBP-CN possesses lowered HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) levels and dramatically increased Tg (glass transition temperature, 162 °C), but unaltered HOMO-LUMO band gap and triplet energy (2.69 eV). Green and red PhOLEDs were fabricated with CBP-CN as hosts for traditional iridium phosphors. The maximum luminance efficiency (ηL) of 80.61 cd A-1 (23.13%) was achieved for the green PhOLED, and 10.67 cd A-1 (15.54%) for the red one, which represent efficiency increases of 25-33% compared with those of the best devices with CBP host and are even among the best data for phosphorescent OLEDs reported so far. The theoretical calculation and the carrier-only devices investigation confirmed that the electron-injecting/-transporting character and the bipolar nature of CBP-CN should be responsible for the performance enhancements. This journal is © 2013 The Royal Society of Chemistry.