Synergistic Passivation With Phenylpropylammonium Bromide for Efficient Inverted Perovskite Solar Cells

Abstract Inverted perovskite solar cells (PSCs) are a promising technology for commercialization due to their reliable operation and scalable fabrication. However, in inverted PSCs, depositing a high‐quality perovskite layer comparable to those realized in normal structures still presents some challenges. Defects at grain boundaries and interfaces between the active layer and carrier extraction layer seriously hinder the power conversion efficiency (PCE) and stability of these cells. In this work, it is shown that synergistic bulk doping and surface treatment of triple‐cation mixed‐halide perovskites with phenylpropylammonium bromine (PPABr) can improve the efficiency and stability of inverted PSCs. The PPABr ligand is effective in eliminating halide vacancy defects and uncoordinated Pb2+ ions at both grain boundaries and interfaces. In addition, a 2D Ruddlesden–Popper (2D‐RP) perovskite capping layer is formed on the surface of 3D perovskite by using PPABr post‐treatment. This 2D‐RP perovskite capping layer possesses a concentrated phase distribution ≈n = 2. This capping layer not only reduces interfacial non‐radiative recombination loss and improves carrier extraction ability but also promotes stability and efficiency. As a result, the inverted PSCs achieve a champion PCE of over 23%, with an open‐circuit voltage as high as 1.15 V and a fill factor of over 83%.