We introduce the use of low temperature sputtered NiOx thin film, which substitutes the PEDOT-PSS and solution-processed NiOx as an effective electron blocking layer for mesoscopic NiO/CHNHPbI perovskite solar cells. The influences of film thickness and oxygen doping on the photovoltaic performances are scrutinized. The cell efficiency has been improved from 9.51 to 10.7% for devices using NiOx fabricated under pure argon atmosphere. With adequate doping under 10% oxygen flow ratio, we achieved power conversion efficiency of 11.6%. The procedure is large area scalable and has the advantage for cost-effective perovskite-based photovoltaics. © 2014 American Chemical Society.