Precise Control of Crystallization and Phase‐Transition with Green Anti‐Solvent in Wide‐Bandgap Perovskite Solar Cells with Open‐Circuit Voltage Exceeding 1.25 V

Abstract Wide‐bandgap perovskite solar cells (PSCs) have attracted a lot of attention due to their application in tandem solar cells. However, the open‐circuit voltage ( V OC ) of wide‐bandgap PSCs is dramatically limited by high defect density existing at the interface and bulk of the perovskite film. Here, an anti‐solvent optimized adduct to control perovskite crystallization strategy that reduces nonradiative recombination and minimizes V OC deficit is proposed. Specifically, an organic solvent with similar dipole moment, isopropanol (IPA) is added into ethyl acetate (EA) anti‐solvent, which is beneficial to form PbI 2 adducts with better crystalline orientation and direct formation of α‐phase perovskite. As a result, EA‐IPA (7‐1) based 1.67 eV PSCs deliver a power conversion efficiency of 20.06% and a V OC of 1.255 V, which is one of the remarkable values for wide‐bandgap around 1.67 eV. The findings provide an effective strategy for controlling crystallization to reduce defect density in PSCs.