Crowning lithium ions in hole transport layer toward stable perovskite solar cells

Abstract

State-of-art perovskite solar cells exhibit comparable power conversion efficiency to silicon photovoltaics. However, the device stability remains a major obstacle that restricts widespread application. Doping hole transport layer induced hygroscopicity, ion diffusion, and use of polar solvent are detrimental factors for performance degradation of perovskite solar cells. Here, we report phase transfer catalyzed LiTFSI doping in Spiro-OMeTAD to address these negative impacts. 12-crown-4 as an efficient phase transfer catalyst promotes the dissolution of LiTFSI without requiring acetonitrile. 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 solar cells deliver enhanced power conversion efficiency and significantly improved stability under humid and thermal conditions compared with the control device. This method can also be applied to dope π-conjugated polymer. Our findings provide a facile avenue to improve the long-term stability of perovskite solar cells.

Rationally designed hole transporting layer system for efficient and stable perovskite solar cells

“…Shen et al introduced 12-Crown-4 as a phase-transfer catalyst to successfully dope the Spiro-OMeTAD layer, promoting dissolution of LiTFSI and increasing device stability. 71 Host-guest interaction between the 12-crown-4 and Li ions promoted the dissolution of LiTFSI dopant without acetonitrile. Also, device stability increased thanks to the formation of larger sized crowned Li ions (crown-ether-Li + complex), which prevented ion migration.…”