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Abstract At present, the dominating electron transport material (ETL) and hole transport material (HTL) used in the state‐of‐the‐art perovskite solar cells (PSCs) are tin oxide and 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)‐9,9′‐spirobifluorene (Spiro‐OMeTAD). However, the surface hydroxyl groups of the SnO 2 layer and the Li + ions within the Spiro‐OMeTAD HTL layer generally cause surface charge recombination and Li + migration, significantly reducing the devices' performance and stability. Here, a molecule bridging layer of 3,5‐bis(fluorosulfonyl)benzoic acid (FBA) is introduced onto the SnO 2 surface, which provides appropriate surface energy, reduces interfacial traps, forms a better energy level alignment, and, most importantly, anchors (immobilizes) Li + ions in the ETL, and consequently improves the device power conversion efficiency (PCE) up to 24.26% without hysteresis. Moreover, the device with the FBA passivation layer shows excellent moisture and operational stability, maintaining over 80% of the initial PCE after 1000 h under both aging conditions. The current work provides a comprehensive understanding of the influence of the extrinsic Li + ion migration within the cell on the device's performance and stability, which helps design and fabricate high‐performance and hysteresis‐free PSCs.
Yin et al. (Wed,) studied this question.