A Volatile Solid Additive Enables Oligothiophene All‐Small‐Molecule Organic Solar Cells with Excellent Commercial Viability

Abstract The commercial viability of all‐small‐molecule (ASM) organic solar cells (OSCs) requires high efficiency, long‐term stability, and low‐cost production. However, satisfying all these factors at the same time remains highly challenging. Herein, a volatile solid additive, namely, 1,8‐dichloronaphthalene (DCN) is demonstrated to simultaneously enhance the power conversion efficiency (PCE) and the storage, thermal as well as photo stabilities of oligothiophene ASM‐OSCs with concise and low‐cost syntheses. The improved PCEs are mainly due to the DCN‐induced morphology control with improved exciton dissociation and reduced non‐geminate recombination. Notably, the PCE of 16.0% stands as the best value for oligothiophene ASM‐OSCs and is among the top values for all types of binary ASM‐OSCs. In addition, devices incorporating DCN have shown remarkable long‐term stability, retaining over 90% of their initial PCE after dark storage aging of 3000 h and thermal or light stressing of 500 h. The findings demonstrate that the volatile‐solid‐additive strategy can be a simple yet effective method of delivering highly efficient and stable oligothiophene ASM‐OSCs with excellent commercial viability.