LAUSR

Abstract Mixed lead halide (Pb(I 1-x Br x ) 2 ) as the seed layer was employed to prepare mixed lead-halide perovskite (MAPbI 3-2x Br 2x , MA = CH 3 NH 3 ) films through two-step sequential deposition method. Ethanol treatment process was also introduced for the control of morphology and microstructure of Pb(I 1-x Br x ) 2 films. The ethanol treatment accelerates the crystallization of Pb(I 1-x Br x ) 2 and the resulted Pb(I 1-x Br x ) 2 films exhibit a porous structure which facilitates more complete conversion of PbI 2 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.