The effect of energy level offset between Ir dopant and carbazole hosts on the emission efficiency

Soonnam Kwon; Kyung-Ryang Wee; Jeong Won Kim; Sang Ook Kang
July 2010
Applied Physics Letters;7/12/2010, Vol. 97 Issue 2, p023309
Academic Journal
The interface energy offsets of various carbazole hosts and iridium(III) [bis(4,6-difluorophenyl) pyridinato-N,C2′]-tetrakis(1-pyrazolyl)borate (FIr6) and their influence on the efficiency were investigated. Vacuum level shifted by +0.12 eV for bis(4-(N-carbazolyl)phenyl)dimethylsilane (Me2SiCBP2) and FIr6 interface, which was negligible for other hosts and FIr6 interface. As a result, the hole injection from the host to the guest was almost barrier free to reach a high efficiency of 17.1% in the Me2SiCBP2 based device. It dropped to 14% when N, N′-dicarbazolyl-3,5-benzene (mCP) was used as the host, which is the reminiscent of the existence of a hole injection barrier (-0.16 eV).


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