Universal and versatile morphology engineering via hot fluorous solvent soaking for organic bulk heterojunction
Tong Shan, Ying Zhang, Yan Wang, Ziyi Xie, Qingyun Wei, Jinqiu Xu, Ming Zhang, Cheng Wang, Qinye Bao, Xin Wang, Chun‐Chao Chen, Jingsong Huang, Qi Chen, Feng Liu, Liwei Chen, Hongliang Zhong
Abstract
After explosive growth of efficiency in organic solar cells (OSCs), achieving ideal morphology of bulk heterojunction remains crucial and challenging for advancing OSCs into consumer market. Herein, by utilizing the amphiphobic nature and temperature-dependent miscibility of fluorous solvent, hot fluorous solvent soaking method is developed to optimize the morphology with various donor/acceptor combinations including polymer/small-molecule, all-polymer and all-small-molecule systems. By immersing blend film into hot fluorous solvent which is utilized as liquid medium with better thermal conductivity, the molecular reorganization is accelerated. Furthermore, fluorous solvent can be miscible with the residue of chloroform and chloronaphthalene above upper critical solution temperature. This mixed solvent diffuses around inside the active layer and selectively promotes molecular reorganization, leading to optimized morphology. Compared to widely-used thermal annealing, this approach processed under mild conditions achieves superior photovoltaic performance, indicating the practicality and universality for morphological optimization in OSCs as well as other optoelectronic devices.