Slowing Down Perovskite Crystallization for Enhanced Open-Circuit Voltage in Wide-Bandgap Perovskite Solar Cells

Controlling crystallization dynamics is essential to mitigating halide segregation and open-circuit voltage (VOC) loss in wide-band gap (WBG) perovskite solar cells (PSCs). Herein, we report a synergistic strategy of crystallization regulation that combines a gas-quenching process with Pb(SCN)2 additive engineering to produce high-quality, high-Br-containing (40%) WBG perovskite films. Compared to the conventional antisolvent method, gas quenching provides a gentler transition to supersaturation, suppresses excessive nucleation, and relieves residual strain. These effects lead to smooth films with large grains, without wrinkles caused by residual stress. Furthermore, Pb(SCN)2 modifies the coordination environment of the precursor solution and promotes the formation of stable intermediate species, which retard grain growth during thermal annealing, as revealed by in situ UV–vis absorption and photoluminescence spectroscopies. Consequently, film quality improves significantly with enhanced crystallographic orientation and suppressed halide segregation, yielding WBG PSCs with an increased VOC from 1.087 to 1.252 V and a power conversion efficiency from 9.24% to 12.82%. This work provides mechanistic insights into the crystallization control of Br-rich WBG perovskites and offers an effective strategy for high-performance perovskite optoelectronic devices.