Mechanistic Study on High Efficiency Deep Blue AIE-Based Organic Light-Emitting Diodes by Magneto-Electroluminescence

作者：Guo, Xiaomin; Yuan, Peisen; Qiao, Xianfeng^*; Yang, Dezhi; Dai, Yanfeng; Sun, Qian; Qin, Anjun; Tang, Ben Zhong^*; Ma, Dongge^*

来源：Advanced Functional Materials, 2020, 30(9): 1908704.

DOI：10.1002/adfm.201908704

• aggregation-induced emission
• deep blue organic light-emitting diodes
• luminescence mechanism
• magnetic field effects

Aggregation-induced emission (AIE) materials are highly attractive because of their excellent properties of high efficiency emission in nondoped organic light-emitting diodes (OLEDs). Therefore, a deep understanding of the working mechanisms, further improving the electroluminescence (EL) efficiency of the resulting AIE-based OLEDs, is necessary. Herein, the conversion process from higher energy triplet state (T-2) to the lowest singlet state (SS1) is found in OLEDs based on a blue AIE material, 4 '-(4-(diphenylamino)phenyl)-5 '-phenyl-[1,1 ':2 ',1 ''-terphenyl]-4-carbonitrile (TPB-AC), obviously relating to the device efficiency, by magneto-EL (MEL) measurements. A special line shape with rise at low field and reduction at high field is observed. The phenomenon is further clarified by theoretical calculations, temperature-dependent MELs, and transient photoluminescence emission properties. On the basis of the T-2-S-1 conversion process, the EL performances of the blue OLEDs based on TPB-AC are further enhanced by introducing a phosphorescence doping emitter in the emitting layer, which effectively regulates the excitons on TPB-AC molecules. The maximum external quantum efficiency (EQE) reaches 7.93% and the EQE keeps 7.57% at the luminance of 1000 cd m(-2). This work establishes a physical insight for designing high-performance AIE materials and devices in the future.