Multifunctional Additives for Performance Improvements in WBG and NBG Perovskite Solar Cells

Abstract Organic–inorganic metal halide perovskite solar cells (PSCs) have reached power conversion efficiencies rivalling established photovoltaic technologies and are already entering commercialization through perovskite‐silicon tandems. However, device stability remains the defining challenge for large‐scale deployment. Although additive engineering is a common approach to improve both efficiency and stability of PSCs, its effectiveness strongly depends on the perovskite composition. Therefore, here stability challenges are discussed for wide bandgap (WBG) and narrow bandgap (NBG) PSCs. In WBG absorbers, minimizing open‐circuit voltage loss and suppressing halide segregation are critical for long term operational stability. In contrast, in the case of NBG absorbers, the critical obstacles to stable performance are difficulties in controlling crystallization dynamics and mitigating Sn ² ⁺ oxidation. Current stability advances in both WBG and NBG PSCs are highlighted, alongside emerging strategies that can drive the next generation of durable PSCs.