Improved Performance of Polymer Bulk Heterojunction Solar Cells Through the Reduction of Phase Separation via Solvent Additives

A high‐boiling‐point additive that favors both poly[(4,4‐didodecyldithieno[3,2‐b:2′,3′‐d]silole)‐2,6‐diyl‐alt‐(2,1,3‐benzoxadiazole)‐4,7‐diyl] and PC71BM in a bulk heterojunction solar cell is used to reduce large‐scale aggregation and phase separation, which increases device performance. This is in contrast to the majority of high‐boiling‐point additives that improve performance by increasing phase separation.