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.