Nonfullerene Ternary Organic Solar Cell with Effective Charge Transfer between Two Acceptors
Cheng Yang, Yang Sun, Qicong Li, Kong Liu, Xiaodi Xue, Yanbin Huang, Kuankuan Ren, Long Li, Yonghai Chen, Zhijie Wang, Zhijie Wang, Shengchun Qu, Zhanguo Wang, Zhanguo Wang
Abstract
High power conversion efficiency can be realized by using a ternary bulk heterojunction with complementary absorption spectra in organic solar cells. However, as the development of nonfullerene acceptors with a broad absorption spectrum makes the absorption efficiency of the photovoltaic devices close to optimal, such a strategy needs modifying. In particular, charge transfer between the two acceptors is necessary to be considered. Herein, we purposely design a ternary system based on PTB7-Th:COi8DFIC:ITIC-4F. Though the presence of ITIC-4F in PTB7-Th:COi8DFIC could not broaden the absorption spectrum obviously, the formed cascade-energy-level alignment is beneficial for promoting and balancing exciton separation and charge transport between the donor and two acceptors and even between the acceptors. Insights into the charge transport route in the completed system are provided via using the techniques including photoluminescence spectroscopy and pump–probe photoconductivity spectroscopy. This work provides a new idea for designing highly efficient ternary organic solar cells.