Mixed lead halide (Pb(I1-xBrx)(2)) as the seed layer was employed to prepare mixed lead-halide perovskite (MAPbI(3-2x)Br(2x), MA = CH3NH3) films through two-step sequential deposition method. Ethanol treatment process was also introduced for the control of morphology and microstructure of Pb(I1-xBrx)(2) films. The ethanol treatment accelerates the crystallization of Pb(I1-xBrx)(2) and the resulted Pb(I1-xBrx)(2) films exhibit a porous structure which facilitates more complete conversion of PbI2 at the same time. As a result, high purity and highly crystallized MAPbI(3-2x)Br(2x) films are obtained. The photovoltaic performance of assembled perovskite solar cells based on MAPbI(3-2x)Br(2x) films are improved upon ethanol treatment and a champion power conversion efficiency (PCE) of 15.53% is obtained with x = 0.2. After exposed in air condition for 14 days, a 86% of initial PCE remains in the champion device. (C) 2017 Elsevier B.V. All rights reserved.