Synergistic Effects of Solid and Solvent Additives on Film Morphology Enable Binary Organic Solar Cells with Efficiency of Over 19%

Abstract Regulating the film morphology features of the photoactive layer is critically important for developing high‐performance organic solar cells (OSCs). Adding solvent or solid additives is widely used to realize fine‐tuned film morphology. However, most high‐performance OSCs are processed only using single component additive, either solvent additive or solid additive. Herein, two structurally similar analogs of 1‐benzothiophene (BT) and benzo[1,2‐b:4,5‐b']dithiophene (BDT) are applied as volatilizable solid additives and are used with the well‐known solvent additive 1‐chloronaphthalene (CN), respectively. Comprehensive morphology analysis revealed that the addition of BT with better volatilization can promote the formation of stronger molecular packing and desirable phase separation, resulting in higher charge mobility and more efficient charge separation. However, the insufficient volatilization of BDT caused excessive aggregation, leading to severe recombination. Consequently, the PMZ‐10:Y6 based binary OSCs treated with the hybrid additives of CN and BT delivered a notable efficiency of 19.03%, which is one of the best values of the Y6‐based binary devices reported so far. Overall, this work highlights the importance of hybrid additive strategy and the reasonable combination of solid and solvent additives in further advancing the development of OSCs field.