Effect of deposition method on the structural and optical properties of CH3NH3PbI3 perovskite thin films

In this study, methyl ammonium lead Iodide perovskite (CH3NH3PbI3 MAPbI(3)) was deposited as a thin planar film on a glass substrate at room temperature using one-step and two-step methods. The effect of each method of preparation on the structural, morphological, and optical properties was investigated. The results show that the average size of the MAPbI(3) crystallites are similar to 57.3 nm and 25.8 nm for the one and two-step methods, respectively. The pore-filling of the perovskite film is incomplete when using the one-step process but completely filled when two-step method was used. Therefore, both one-step and two-step methods lead to perovskite islands and void-free perovskite layers, respectively. Scanning emission microscopy images show that the quality of the film produced by two-step is much better than that formed via one-step. Moreover, the perovskite film prepared via one-step method tends to produce a higher pinhole density than two-step, and thus lower coverage that leads to a low absorption and a low absorption coefficient. Parameters such as optical absorption coefficient, refractive index, extinction coefficient, dielectric constant, and optical conductivity were also estimated. The intensities of both photoluminescence and amplified spontaneous emission spectra of MAPbI(3) sample prepared via one-step method were found to be lower than those prepared via two-step.