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High-Performance Non-doped Blue OLEDs based on Efficiently Triplet-Triplet Upconversion and Aggregation-induced Emission
preprintsubmitted on 10.01.2021, 03:09 and posted on 20.01.2021, 12:49 by Pengbo Han, Chengwei Lin, Kaojin Wang, Yanping Qiu, Haozhong Wu, Dongge Ma, Anjun Qin, Ben Zhong Tang
Triplet-triplet upconversion (TTU), where two low-energy triplet excitons are converted to one higher energy singlet exciton, is excellent approach to break through the theoretical limit of the pure ﬂuorescent organic light-emitting diodes (OLEDs) by 5%. To data, however, the reported emitters with high emission efficiency and efficiently TTU in film state are rare. Herein, we design the blue aggregation-induced emission luminogens (AIEgens) and investigate their upconversion efficiency. TPA-An-mPhCz can not only achieve high emission efficiency in the film state, but also show high upconversion efficiency of close to 50% even though the calculated energy level of the triplet excitons (T2) is lower than 2T1. A possible upconversion mechanism is proposed according to the transient electroluminescence spectra and theoretical calculation. This strategy may provide a new platform for the construction of highly efficient non-doped blue OLEDs based on TTU and AIEgens.