High‐Efficiency and Stable FAPbBr ₃ Perovskite Solar Cells Enabled by 3,7‐POPA: A Multifunctional Phenoxazine‐Based Self‐Assembled Monolayers

Abstract While self‐assembled monolayers (SAMs) have demonstrated remarkable success in iodide‐based perovskite solar cells (PSCs), their application in bromide‐based PSCs is fundamentally constrained by poor crystallization behavior and interfacial energy level misalignment. To overcome these limitations, the SAMs of (3‐(3,7‐bis(diphenylphosphoryl)‐10H‐phenoxazin‐10‐yl)propyl) phosphonic acid (3,7‐POPA) are designed and synthesized to address these challenges in FAPbBr 3 ‐based PSCs. 3,7‐POPA not only facilitates oriented crystallization of perovskite and defect minimization but also optimizes energy level alignment at the hole‐selective interface, thereby significantly enhancing hole extraction efficiency. Consequently, optimized FAPbBr 3 ‐based PSCs achieve a power conversion efficiency (PCE) of 10.79% with a record open circuit voltage (Voc) of 1.51 V. Remarkably, after operating at maximum power point for 1000 h, the encapsulated device maintains 90% of its initial PCE. The novel SAM‐based hole transport strategy simultaneously resolves crystallization, defect, and energy‐level challenges in Br‐based PSCs, achieving record efficiency and stability for high‐performance PSCs.