Electric field-induced hole injection-enhanced photoluminescence in a N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine-based emitter
Xu-Xie Hui-Na (许谢慧娜), Li Wen-Bin (李文彬), Peng Huan (彭欢), He Yun (何鋆), Yu Hao-Miao (于浩淼), Hou Xiao-Yuan (侯晓远)
Key Laboratory of Micro-and Nano-Photonic Structures (Ministry of Education) and State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
Abstract Non-monotonic, asymmetrical electric field dependence of photoluminescence (PL) intensity is observed in a monolayer sample of tris-(8-hydroxyquinoline) aluminum (AlQ) doped N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine (TPD). A possible model is proposed: the charge separation from the dissociated photoexcited excitons causes energy band bending in the organic films and improves the hole injection from the electrode, which brings about the extra fluorescence. This mechanism is further verified by a series of experiments using a series of samples, variously featuring symmetrical electrodes, block layers, and hosts with lower hole mobilities.
Fund: Project supported by the National Natural Science Foundation of China (Grant No. 11134002) and the National Science and Technology MajorProject of the Ministry of Science and Technology of China (Grant No. 2012CB921401).
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