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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. [ABSTRACT FROM AUTHOR]

Molecular doping is often used in organic semiconductors to tune their (opto)electronic properties. Despite its versatility, however, its application in organic photovoltaics (OPVs) remains limited and restricted to p‐type dopants. In an effort to control the charge transport within the bulk‐heterojunction (BHJ) of OPVs, the n‐type dopant benzyl viologen (BV) is incorporated in a BHJ composed of the donor polymer PM6 and the small‐molecule acceptor IT‐4F. The power conversion efficiency (PCE) of the cells is found to increase from 13.2% to 14.4% upon addition of 0.004 wt% BV. Analysis of the photoactive materials and devices reveals that BV acts simultaneously as n‐type dopant and microstructure modifier for the BHJ. Under optimal BV concentrations, these synergistic effects result in balanced hole and electron mobilities, higher absorption coefficients and increased charge‐carrier density within the BHJ, while significantly extending the cells' shelf‐lifetime. The n‐type doping strategy is applied to five additional BHJ systems, for which similarly remarkable performance improvements are obtained. OPVs of particular interest are based on the ternary PM6:Y6:PC71BM:BV(0.004 wt%) blend for which a maximum PCE of 17.1%, is obtained. The effectiveness of the n‐doping strategy highlights electron transport in NFA‐based OPVs as being a key issue. [ABSTRACT FROM AUTHOR]