Morphology and composition control of the perovskite thin films are of importance to develop high efficient perovskite solar cells. Previously, my group has demonstrated a 13% power conversion efficiency perovskite solar cells using two-step ultrasonic spray techniques. In this talk, I will present our attempts to optimize the perovskite thin film crystallinity and composition. Seed growth method is introduced to grow platelet nanostructured PbI2 thin film on organic transport layer PEDOT:PSS. The platelet PbI2 is discovered to be more effectively converted into perovskite films when subject to sprayed droplets of methylammonium, which enables a thicker perovskite to be formed with less unreacted PbI2, compared to those converted from compact PbI2 thin films. The influence of adding MABr in the PbI2 solution on the resulting solar cells will also be presented.