Among the 3D organic-inorganic hybrid perovskite (OIHP), mixed formamidinium and methylammonium cations lead iodide is one of the most promising for solar cell application. After optimizing the use of methylammonium chloride (MACl) additive for the preparation of compact, high quality and large crystal grain layers made of pure α-phase perovskite with FA0.94MA0.06PbI3 composition, the treatment of the perovskite surface by a 2-Phenylethylamonium iodide (PEAI) solution has been implemented. This treatment, without any thermal annealing, leads notably to the spontaneous formation of a crystallized (PEA)2PbI4 2D-perovskite nanolayer at the film surface due to partial organic cation dissolution. This buffer layer is shown to favor a fast transfer of the holes towards the HTL and to reduce the recombinations at T. Zhu, D. Zheng, J. Liu, L. Coolen, Th. Pauporté, ACS Appl. Mater. Interfaces 12 (2020) 37197−37207 2 and near the perovskite/HTL interface in perovskite solar cells (PSCs). It is shown to boost their maximum power conversion efficiency (PCE) from 20.37% to 22.18% while the hysteresis becomes negligible. A comprehensive study of the device electrical response has been performed. The electrical impedance spectroscopy (EIS) measurements have been fitted with ad-hoc equivalent electrical circuits. The electrical responses due to interface stabilization, the intrinsic dielectric relaxation of the perovskite, the charge depletion and charge recombinations have been distinguished. The low frequency capacitance is analyzed as a charge recombination capacitance. The perovskite surface buffer layer is notably shown to supress charge recombinations from the boosting of the high frequency and low frequency recombination resistances as well as from the marked decrease of the low frequency recombination capacitance. The prepared devices are proved especially resistant to electrical stresses, to light irradiation and to moisture.