摘要： Recently, nickel oxide (NiOx) thin films have been used as an efficient and robust hole transport layer (HTL) in inverted planar perovskite solar cells (IP-PSCs) to replace costly and unstable organic transport materials. However, the power conversion efficiency (PCE) of most IP-PSCs using NiOx HTLs is rather limited below 20 % due to insufficient electronic conductivity of the NiOx. In this work, solution-processed Al-doped NiOx (ANO) films are suggested as HTLs for low cost and stable IP-PSCs. The electrical conductivity of the NiOx film is significantly enhanced by the Al doping which effectively reduces the non-radiative recombination losses at the HTL(cid:150)perovskite interfaces and boosts hole extraction/transportation. The device with undoped NiOx shows the best PCE of 16.56 %, whereas ANO HTL (5 % doping) contributes to achieve a PCE of 20.84 %, which outperforms other CH3NH3PbI3 IP-PSCs with NiOx-based HTLs reported to date. Moreover, a reliability test (1728 h storage) shows that the performance stability is enhanced by approximately 11 % by employing ANO HTLs. This investigation into ANO HTLs provides a new guideline for the further development of highly efficient and reliable IP-PSCs using low cost and robust metal oxide HTLs.