A Nontoxic Bifunctional (Anti)Solvent as Digestive‐Ripening Agent for High‐Performance Perovskite Solar Cells

The preparation of high-quality perovskite films is important for achieving high-performance perovskite solar cells (PSCs). The effective balance between solvent and antisolvent is an essential factor for regulating high-quality perovskite film during the spin-coating and thermal-annealing steps. In this work, a greener, nonhalogenated, nontoxic bifunctional (anti)solvent, methyl benzoate (MB), is developed not only as an antisolvent to rapidly generate crystal seeds at the perovskite spin-coating step, but also as a digestive-ripening solvent for the perovskite precursors, which can prevent the loss of organic components during the thermal-annealing stage and effectively suppress the formation of miscellaneous lead halide phases. As a result, this novel bifunctional (anti)solvent is employed in planar n-i-p PSCs for engineering high-quality perovskite layers and thus achieving a power conversion efficiency up to 22.37% with negligible hysteresis and >1300 h stability. Moreover, due to the high boiling point and low-volatility characteristic of MB, high-performance PSCs are achieved reproducibly at different operating temperatures (22-34 °C). Therefore, this developed bifunctional solvent system can provide a promising platform toward globally upscaling and commercializing PSCs in all seasons and regions.