Overcoming the Voltage Deficit in Hybrid‐Processed Wide‐Bandgap Perovskite Solar Cells

ABSTRACT Hybrid perovskite fabrication routes offer a promising pathway toward scalable and conformable photovoltaic technologies, particularly for perovskite/Si tandem integration. However, hybrid‐processed wide‐bandgap (WBG) perovskites have consistently suffered from a pronounced open‐circuit voltage (V _oc ) deficit compared with solution‐processed counterparts, limiting their practical relevance. Here, we identify two coupled origins of the voltage deficit in this system: diffusion‐limited conversion, which causes incomplete and vertically inhomogeneous crystallization, and interfacial non‐radiative recombination. Methylammonium chloride (MACl) is introduced to regulate the diffusion‐driven conversion and improve vertical halide homogeneity, while bifacial passivation reduces recombination losses and optimizes energy alignment at both charge‐transport interfaces. As a result, hybrid‐processed WBG perovskite solar cells (PCSs) achieve a record V _oc of 1.269 V, approaching 90% of the radiative limit for a 1.7 eV bandgap, and a PCE of 21%, the highest reported among p–i–n devices with the same bandgap across all deposition routes. The performance is well maintained under low‐injection conditions and in 1 cm ² large‐area devices, demonstrating the robustness and scalability of this strategy. These results show that the long‐standing voltage deficit in the hybrid process is not intrinsic, but can be overcome through coupled control of crystallization and interfaces, establishing a viable pathway toward high‐efficiency tandem photovoltaics.