Reversible crosslinking strategy for dynamic strain regulation in inverted perovskite solar cells

Perovskite solar cells tend to degrade much faster under day-night cycling conditions. One key reason lies in the periodic strain in perovskite film under cycling mode due to its soft crystal lattice nature. Here, we propose a dynamic reversible crosslinking strategy by introducing disulfide-mediated cross-linkable additive of 2-methacryloyloxyethyl-thioctate. Combining with carbon-carbon double bond, 2-methacryloyloxyethyl-thioctate crosslinks at grain boundaries at high temperature through disulfide bond ring-opening, inhibiting perovskite expansion under day conditions. While at room temperature, 2-methacryloyloxyethyl-thioctate de-crosslinks with inverse ring-closing reaction, promoting perovskite recovery under night conditions. As a result, periodic film strain is alleviated in PSCs during day-night cycling aging. Resulting devices show high efficiency of 26.5% with good cycling stability, retaining 95.7% of initial efficiency after MPP tracking for 1,800 h under day-night cycling mode.