Crowning Lithium Ions in Hole‐Transport Layer toward Stable Perovskite Solar Cells
Ying Shen, Kaimo Deng, Qinghua Chen, Gui Gao, Liang Li
Abstract
Abstract State‐of‐the‐art perovskite solar cells (PSCs) exhibit comparable power conversion efficiency (PCE) to that of silicon photovoltaic devices. However, the device stability remains a major obstacle that restricts widespread application. Doping‐induced hygroscopicity, ion diffusion, and use of polar solvents in the hole‐transport layer are detrimental factors for performance degradation of PSCs. Here, phase‐transfer‐catalyzed LiTFSI doping in Spiro‐OMeTAD is developed to address these negative impacts. 12‐Crown‐4 as an efficient phase‐transfer catalyst promotes the dissolution of LiTFSI without requiring acetonitrile. A combined experimental and theoretical study demonstrates the host–guest interaction between Li + ions and 12‐crown‐4. Crowning Li + ions by forming more stable and less diffusive crown‐ether–Li + complexes retards the generation of hygroscopic lithium oxides and mitigates Li + ‐ion migration. Optimized PSCs deliver enhanced PCE and significantly improved stability under humid and thermal conditions compared with a control device. This method can also be applied to dope π‐conjugated polymer. The findings provide a facile avenue to improve the long‐term stability of PSCs.