Professor Philip Chow of the Department of Mechanical Engineering and his team worked on the research for the topic “The role of interfacial donor–acceptor percolation in efficient and stable all-polymer solar cells”. The research findings were recently published in Nature Communications on February 8, 2024.
Details of the publication:
The role of interfacial donor–acceptor percolation in efficient and stable all-polymer solar cells
Zhen Wang, Yu Guo, Xianzhao Liu, Wenchao Shu, Guangchao Han, Kan Ding, Subhrangsu Mukherjee, Nan Zhang, Hin-Lap Yip, Yuanping Yi, Harald Ade, Philip C. Y. Chow, article in Nature Communications
https://www.nature.com/articles/s41467-024-45455-0
Abstract
Polymerization of Y6-type acceptor molecules leads to bulk-heterojunction organic solar cells with both high power-conversion efficiency and device stability, but the underlying mechanism remains unclear. Here we show that the exciton recombination dynamics of polymerized Y6-type acceptors (Y6-PAs) strongly depends on the degree of aggregation. While the fast exciton recombination rate in aggregated Y6-PA competes with electron-hole separation at the donor–acceptor (D–A) interface, the much-suppressed exciton recombination rate in dispersed Y6-PA is sufficient to allow efficient free charge generation. Indeed, our experimental results and theoretical simulations reveal that Y6-PAs have larger miscibility with the donor polymer than Y6-type small molecular acceptors, leading to D–A percolation that effectively prevents the formation of Y6-PA aggregates at the interface. Besides enabling high charge generation efficiency, the interfacial D–A percolation also improves the thermodynamic stability of the blend morphology, as evident by the reduced device “burn-in” loss upon solar illumination.