摘要： The efficiency of perovskite solar cells (PSCs) developed rapidly in recent years, but the stability still lagged behind. Ion migration effect, especially from the small methylammonium (MA) cations, is a main factor for stability issues and MA-free perovskite is one appreciated pathway to suppress ion migration. In this work, we reveal there is a much lower valence band maximum (VBM) of -5.8 eV for the most studied MA-free perovskite of FA0.83Cs0.17PbI2.7Br0.3, which is much different from traditional perovskite and the huge energy level mismatch between perovskite and hole transport layer (HTL) is a main factor to limit the device performance of MA-free PSCs. It is found doping with conjugated polyelectrolyte of poly[(9,9-bis(3’-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN-Br) in perovskite can significantly promote anode contact and result in better device performance as well as stability of FA0.83Cs0.17PbI2.7Br0.3 based MA-free PSCs in inverted planar structure. The PFN-Br arise the energy position of VBM of perovskite and results in well-matched energy levels between perovskite and HTL of poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine (PTAA). Carrier extraction and transportation are highly encouraged at the surface of PTAA / perovskite, and the corresponding interface recombination is effectively suppressed. As a result, a 60mV increased VOC is achieved, which promotes champion device efficiency to 20.32%. At the same time, the efficient device displays a significant stability under continuous illumination and bias at MPP conditions, which could remain 80% of its initial power conversion efficiency (PCE) under continuous operation under one sun illumination over 500 hours.