Oxidant-Assisted Interface Engineering for Enhanced Stability in Lead Halide Perovskite Solar Cells

The presence of excess lead iodide (PbI₂) in lead halide perovskites can accelerate solar cell degradation. Under illumination, PbI₂ readily undergoes photodecomposition, producing metallic lead (Pb⁰) that introduces deep trap states and iodine (I₂) that destabilizes the bandgap and phase stability, particularly for the α phase of FAPbI₃. To mitigate these phenomena, we demonstrate a proof-of-concept approach by introducing potassium bromate (KBrO₃), an oxidizing agent, between the metal oxide electron transport layer (ETL) and the FAPbI₃ perovskite layer. It suppresses the excessive formation and photoinduced decomposition of PbI₂ by enhancing the crystallinity of the perovskite layer and passivating the undercoordinated lead with internal oxygen sources. The resulting KBrO₃-treated device achieved a power conversion efficiency (PCE) of 24.10% with respect to 21.21% of that of the control sample. Importantly, the operational stability, tested following the ISOS-L-1 protocol, is enhanced with the device maintaining 86% of its initial PCE after 1000 h. This study suggests a new perspective for improving photostability in Pb-based perovskite films.