State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electron Science and Technology of China (UESTC), Chengdu 610054, China
Yellow organic light-emitting devices (YOLEDs) with a novel structure of ITO/MoO3(5 nm)/NPB(40 nm)/TCTA(15 nm)/CBP:(tbt)2Ir(acac)(x%)(25 nm)/FIrpic(y nm)/TPBi(35 nm)/Mg:Ag are fabricated. The ultrathin blue phosphorescent bis[(4,6-difluorophenyl)-pyridi-nato-N,C2\prime ](picolinate) iridium (III) (FIrpic) layer is regarded as a high-performance modification layer. By adjusting the thickness of FIrpic and the concentration of (tbt)2Ir(acac), a YOLED achieves a high luminance of 41618 cd/m2, power efficiency of 49.7 lm/W, current efficiency of 67.3 cd/A, external quantum efficiency (EQE) of 18%, and a low efficiency roll-off at high luminance. The results show that phosphorescent material of FIrpic plays a significant role in improving YOLED performance. The ultrathin FIrpic modification layer blocks excitons in EML. In the meantime, the high triplet energy of FIrpic (2.75 eV) alleviates the exciton energy transport from EML to FIrpic.
Project supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 61675041 and 61605253), the Foundation for Innovation Research Groups of the NSFC (Grant No. 61421002), and the Fund from the Science & Technology Department of Sichuan Province, China (Grant No. 2016HH0027).
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