Fluorination-driven optimization of non-fused small molecular acceptors for high-efficiency organic solar cells

Abstract

Organic solar cells (OSCs) represent a promising technology in the renewable energy sector, with non-fused small molecular acceptors (SMAs) emerging as efficient alternatives to traditional fused counterparts. This study focuses on the design and synthesis of three pairs of non-fused SMAs, ETC-0F, ETC-1F, and ETC-3F, featuring varying degrees of fluorination in the thiophene ethyl ester side chains. By systematically varying the fluorination levels, we investigate the impact on film morphology, molecular structure, and optoelectronic properties in OSCs. The devices based on the synthesized SMAs were characterized for their power conversion efficiencies (PCEs), revealing that the ETC-1F-based device obtained the best efficiency of 12.66%, surpassing 11.70% for the ETC-0F-based device and significantly outperforming the ETC-3F-based OSC (9.23%). The enhanced efficiency of the ETC-1F device is attributed to a balanced optimization of molecular interactions and phase separation within the active layer, promoting favorable molecular packing and efficient charge transport while reducing energy losses. The results underscore the potential of selective fluorination as a powerful strategy for designing highly efficient non-fused SMAs, paving the way for more efficient OSCs with simpler synthesis pathways.