Stannic oxide , Sn (IV) O2 synthesized by the sol-gel method showed heterogeneous crystallinity involving traces of stannous oxide, Sn (II) O as well which were studied based on the nucleation sites and aggregation of crystallites. The height to width ratio (HWR) was found to be an effective means of analyzing the growth process which involved lateral atomic diffusion and reversible phase transitions. The crystallinity and aggregation to larger crystallites is beneficial for electron transfer layer (ETL) in perovskite solar cells. The structure and morphology were determined by XRD and SEM-EDAX