In this paper, a novel one-step solution approach is developed to prepare high quality methylammonium lead trihalide (MAPbI(3)) perovskite films. This approach employs methanol as additive, which is added into the perovskite precursor solution. The use of methanol can enhance the absorption of MAPbI(3) and significantly improve the coverage of MAPbI(3) on a planar substrate. The fabricated perovskite solar cell (PSC) with methanol exhibits a higher power conversion efficiency (PCE) compared with that without methanol (19.51% vs 16.53%). Furthermore, the power conversion efficiencies of devices with methanol are still high after kept in dark under ambient environment for 30 days. This work provides a method to prepare high quality perovskite films for planar perovskite solar cells with high performance. (c) 2018 Elsevier Ltd. All rights reserved.