Two novel bipolar compounds based-on 1, 2, 4-triazol derivatives for non-doped deep-blue and green phosphorescent OLED applications

Utilizing 2-(2-phenyl-2H-1,2,4-triazol-3-yl)pyridine (TAZ) as acceptor, two novel bipolar materials were designed and synthesized, one using triphenylamine (TPA) as donor and named as TAZ-TPA, and the second one using 9,9-diphenyl-9H-fluorene (DPPF) as donor and denoted as TAZ-DPPF. The different donors result in the various photophysical natures. The compound of TAZ-TPA possesses high thermal stabilities with a glass transition temperature (T-g) of 145 degrees C and shows a strong deep-blue emission at 435 nm in CH2Cl2 solution. The non-doped device utilizing TAZ-TPA as emitter exhibits excellent stability with the Commission Internation de L'Eclairage coordinates of (0.15, 0.05). The radiative exciton yield of 36% in TAZ-TPA device is obtained due to the occurrence of charge transfer and hybridized local and charge-transfer excited states. The PL spectrum of TAZ-DPPF locates in the ultraviolet range with the peaks at 384 and 377 nm, and only the local electron excited state is observed. The green phosphorescent OLED hosted by TAZ-DPPF has achieved the performance of the current efficiency at 45.0 cd/A. (C) 2017 Elsevier Ltd. All rights reserved.