Non‐halogenated Solvent‐Processed Organic Solar Cells with Approaching 20 % Efficiency and Improved Photostability

Abstract The development of high‐efficiency organic solar cells (OSCs) processed from non‐halogenated solvents is crucially important for their scale‐up industry production. However, owing to the difficulty of regulating molecular aggregation, there is a huge efficiency gap between non‐halogenated and halogenated solvent processed OSCs. Herein, we fabricate o ‐xylene processed OSCs with approaching 20 % efficiency by incorporating a trimeric guest acceptor named Tri‐V into the PM6:L8‐BO‐X host blend. The incorporation of Tri‐V effectively restricts the excessive aggregation of L8‐BO‐X, regulates the molecular packing and optimizes the phase‐separation morphology, which leads to mitigated trap density states, reduced energy loss and suppressed charge recombination. Consequently, the PM6:L8‐BO‐X:Tri‐V‐based device achieves an efficiency of 19.82 %, representing the highest efficiency for non‐halogenated solvent‐processed OSCs reported to date. Noticeably, with the addition of Tri‐V, the ternary device shows an improved photostability than binary PM6:L8‐BO‐X‐based device, and maintains 80 % of the initial efficiency after continuous illumination for 1380 h. This work provides a feasible approach for fabricating high‐efficiency, stable, eco‐friendly OSCs, and sheds new light on the large‐scale industrial production of OSCs.