 The two-step coding method of CH3NH3PBI3 light absorber on a mesoporous TiO2 layer results in higher average power conversion efficiency, 13.9%, compared to the one-step coding method, 7.5%, with coverage, poor filling, and morphology being critical factors affecting photovoltaic performance. This article was authored by John Hayakam, Huisi and Kim, and Namdu Park.