Dynamic recombination of triplet excitons in polymer heterojunctions
Ya-Dong Wang(王亚东)1, †, Jian-Jun Liu(刘建军)1, Xi-Ru Wang(王溪如)2, Yan-Xia Liu(刘艳霞)1, and Yan Meng(孟艳)3, ‡
1 College of Information Science and Engineering, Hebei North University, Zhangjiakou 075000, China 2 Department of Electronics, Polytech Nice Sophia, Nice 06200, France 3 Department of Physics, Xingtai University, Xingtai 054001, China
The dynamic recombination of two triplet excitons with opposite spins in the heterojunction structure has been investigated using a nonadiabatic evolution method. We demonstrate that luminous composite states including the excited polaron and the biexciton can be formed efficiently via the triplet exciton–triplet exciton reaction in the heterojunction and therefore this reaction can enhance the electroluminescence efficiency considerably, which is consistent qualitatively with experimental observations. Meanwhile, we find that, although the heterojunctions are beneficial to the generation of luminescent particles, large band offset caused by the heterojunction structure is not helpful to improve the electroluminescence efficiency. In addition, the mechanism of the triplet exciton–triplet exciton reaction in heterojunction is different from that of two similar coupling chains. Our results may deepen the understanding of the electroluminescence mechanism in polymer light-emitting devices.
Received: 11 May 2020
Revised: 08 June 2020
Accepted manuscript online: 12 June 2020
Fund: the National Natural Science Foundation of China (Grant No. 11347171), the Doctoral Foundation (Grant No. 12995563), and the Research Fund (Grant No. YB2018026) from Hebei North University.
Ya-Dong Wang(王亚东), Jian-Jun Liu(刘建军), Xi-Ru Wang(王溪如), Yan-Xia Liu(刘艳霞), and Yan Meng(孟艳) Dynamic recombination of triplet excitons in polymer heterojunctions 2020 Chin. Phys. B 29 117101
Fig. 1.
Schematic diagrams of the polymer heterojunction structure (a) and its energy spectrum (b).
Fig. 2.
Temporal evolution of the lattice configuration for the recombination processes between two triplet excitons with different interchain interactions: t1 = 0.1 eV (top panel); t1 = 0.18 eV (bottom panel). The unit of the third axis vertical to the time and site index is 10–1 nm.
Fig. 3.
Evolutions of the localized electronic energy levels (a) and their occupied numbers (b) with time, t1 = 0.1 eV (from the same simulation as the top panel of Fig. 2).
Fig. 4.
The schematic diagram of resultant states for the recombination processes between two triplet excitons.
Fig. 5.
Evolutions of the localized electronic energy levels (a) and their occupied numbers (b) with time, t1 = 0.18 eV (from the same simulation as the bottom panel of Fig. 2).
Fig. 6.
Dependence of yields for states (b), (c) and (d) on the interchain interactions for the recombination process between two triplet excitons.
Fig. 7.
Dependence of yields for states (b), (c) and (d) on the band offset for the recombination process between two triplet excitons.
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