Unordered aggregation of perovskite particles on TiO2 mesoporous film surface is a common problem in
one-step solution process for fabricating perovskite solar cells (PSCs). This phenomenon is harmful for
homogeneous dispersion of perovskite in mesoporous TiO2 film and responsible for the low photovoltaic
performance of corresponding perovskite solar cells at the same time. Delicate control of perovskite
nucleation and growth is an effective route to solve this problem. In this work, we proposed a facile
strategy to improve perovskite (CH3NH3PbI3) growth by adding C6H5CH2NH3I (BAI) or NH4I ionic compounds
in perovskite precursor solution. We investigated perovskite crystal structure and morphology,
optical and electrochemical properties of perovskite films or devices using different additives by XRD,
SEM, UVeVis, IPCE, and EIS. We found that these additives could decrease the grain size of perovskite
crystal and diminish perovskite particle aggregation on TiO2 film surface. This effect is benefit for
electron transfer on perovskite/TiO2 interface. Finally, perovskite solar cells using BAI or NH4I additives
obtain the best solar-to-electricity conversion efficiency of 9.05% and 9.49%, respectively, which are much
higher than that of the pristine one, 6.83%.