Carrier Transport in CH3NH3PbI3 Films with Different Thickness for Perovskite Solar Cells

The typical broad absorption features have enabled halide perovskite to be a promising candidate of the next generational solar cell materials. However, the fundamental properties, upon which the photoelectric performance of perovskite device is based, are currently still not clear. Herein, the photovoltaic efficiencies in perovskite films with various thicknesses have been investigated to reveal a direct correlation between internal structure factors, such as crystal orientation, grain size, and photoelectric performance of perovskite films. It is found that the photovoltaic efficiency of perovskite films, especially with the optimal thickness around 300 nm, is significantly increased, which can be ascribed to the improved carrier transport properties resulting from the preferred crystal structure. When the film thickness diverges from 300 nm, the extra charge recombination with decreasing mobility leads to the reduction of photovoltaic efficiency again in perovskite solar cells. These results demonstrate crystal structure as one of the decisive roles in device properties, which are helpful to improve photovoltaic performance of perovskite solar cells.