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

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.