The control of surface texture for planar CH3NH3PbI3−xClx film and its effect on photovoltaic performance

The surface texture with a long alignment was observed on the surface of CH3NH3PbI3−xClx films prepared using one-step solution deposition. We found that it appears only when hydroiodic acid with stabilizer H3PO2 is adopted to prepare CH3NH3I powder. However, even with this stabilizer, the surface texture of CH3NH3PbI3−xClx films can also be eliminated completely by sufficiently lateral diffusion before annealing, which can be achieved by high speed coating above 3000 rpm or drying for 30 min at room temperature. The later process results in a smooth surface with homogeneous grains and hence the improvement of photovoltaic performance.