Inverted perovskite solar cells (PSCs) are a promising technology forcommercialization due to their reliable operation and scalable fabrication.However, in inverted PSCs, depositing a high-quality perovskite layercomparable to those realized in normal structures still presents somechallenges. Defects at grain boundaries and interfaces between the activelayer and carrier extraction layer seriously hinder the power conversionefficiency (PCE) and stability of these cells. In this work, it is shown thatsynergistic bulk doping and surface treatment of triple-cation mixed-halideperovskites with phenylpropylammonium bromine (PPABr) can improve theefficiency and stability of inverted PSCs. The PPABr ligand is effective ineliminating halide vacancy defects and uncoordinated Pb2+ions at both grainboundaries and interfaces. In addition, a 2D Ruddlesden–Popper (2D-RP)perovskite capping layer is formed on the surface of 3D perovskite by usingPPABr post-treatment. This 2D-RP perovskite capping layer possesses aconcentrated phase distribution≈n=2. This capping layer not only reducesinterfacial non-radiative recombination loss and improves carrier extractionability but also promotes stability and efficiency. As a result, the inverted PSCsachieve a champion PCE of over 23%, with an open-circuit voltage as high as1.15 V and a fill factor of over 83%.