Effective Preparation of Nanoscale CH 3 NH 3 PbI 3 Perovskite Photosensitizers for Mesoporous TiO 2 ‐Based Solar Cells by Successive Precursor Layer Adsorption and Reaction Process

Nanoscale CH 3 NH 3 PbI 3 perovskite sensitizers are grown by delivering each precursor successively onto the surface of mesoporous (meso) TiO 2 electrodes. Using Pb(NO 3 ) 2 ions as a lead(II) source and CH 3 NH 3 I (MAI) for methylammonium and iodide sources, repetitive cycles of the two dipping steps are successful in growing few nanometer‐sized MAPbI 3 gradually on the TiO 2 surface inside the meso‐TiO 2 film. However, some aggregates are observed on the top surface of the meso‐TiO 2 film due to slight dissolution of PbI 2 and its accumulation/reaction with MAI at the top surface of the meso‐TiO 2 film. To solve this inhomogeneity of the deposition, a nondestructive multiple deposition route for nanoscale MAPbI 3 is suggested as a successive precursor layer adsorption and reaction (SPLAR) process where, from the second cycle of deposition, PbI 2 is delivered with the help of an ionic liquid compound dissolved in dichloromethane. With this new Pb precursor in less‐polar solvents, nanoscale MAPbI 3 sensitizers are grown without dissolution of preformed perovskites or formation of some aggregates at the top surface. After the third cycle of SPLAR deposition, about 7.0 nm–sized MAPbI 3 sensitizers are prepared and display enhanced photovoltaic performance (7.18 ± 0.31%) compared with devices obtained from only one cycle (5.74 ± 0.30%).