In this paper, we demonstrate the high-performance inverted planar heterojunction perovskite solar cells (PeSCs) based on the novel inorganic hole-transporting layer (HTL) of silver (Ag)-doped NiOx (Ag: NiOx). Density-functional theory (DFT) calculation reveals that Ag prefers to occupy the substitutional Ni site (Ag-Ni) and behaves as an acceptor in NiO lattice. Compared with the pristine NiOx films, appropriate Ag doping can increase the optical transparency, work function, electrical conductivity and hole mobility of NiOx films. Moreover, the CH3NH3PbI3 perovskite films grown on Ag: NiOx exhibit better crystallinity, higher coverage and smoother surface with densely packed larger grains than those grown on the pristine NiOx film. Consequently, the Ag: NiOx HTL boosts the efficiency of the inverted planar heterojunction PeSCs from 13.46% (for the pristine NiOx-based device) to 16.86% (for the 2 at.% Ag: NiOx-based device). Furthermore, the environmental stability of PeSCs based on Ag: NiOx HTL is dramatically improved compared to devices based on organic HTLs and pristine NiOx HTLs. This work provides a simple and effective HTL material system for high-efficient and stable PeSCs. (C) 2017 Elsevier B.V. All rights reserved.