Synergistic Regulation of Crystallization Kinetics of Donor/Acceptor by New Volatile Additives for High Performance Organic Solar Cells

Abstract Ideal nanoscale morphology of heterojunction active layer is important for the development of organic solar cells (OSCs). However, the mismatched crystalline kinetic between the polymer donor and small molecular acceptor often leads to the difficulties in controlling the morphology of the active layer. Herein, polar 1,2‐dibromo‐4,5‐difluorobenzene (DFB) and non‐polar 1,4‐dibromotetrafluorobenzene (TFB) are developed as the volatile additives for OSCs. More attractively, different from the reported volatile additives, both new volatile additives can simultaneously interact with donor and acceptor, synergistic regulating the crystallization kinetic and well‐balancing the crystallization behaviors between the polymer donor and small molecular acceptor during film formation process. Notably, due to the stronger dipole‐dipole interactions with active layer, polar DFB induces the more favorable film morphology than non‐polar TFB. As a result, the two additives‐treated PM6:Y6 devices both outperform the CN‐treated device (16.13%), and the polar DFB‐treated device deliver a higher efficiency of 17.15% than non‐polar TFB‐treated one (16.30%). With polar DFB additive, PM6:L8‐BO and PM6: BTP‐eC9 also achieve superior efficiency of 18.46% and 18.17%, respectively. This work deepens the insights of regulating crystallization kinetics and optimizing nanoscale morphology by developing simple volatile additives for further achieving high‐efficient OSCs.