Synthesis and investigation of the properties of organic-inorganic perovskite films with non-contact optical methods

Abstract

Presented in this work are the results of our study of the photoelectric properties of perovskite $CH_3NH_3PbI_{2.98}Cl_{0.02}$ films deposited on a glass substrate using the spin-coating method. The unit cell parameters of the perovskite are determined using x-ray diffractometry. It is shown that the film morphology represents a net of non-oriented needle-like structures with significant roughness and porosity. In order to investigate the properties of the films obtained, non-contact methods were used, such as transmission and reflection measurements and the measurements of the spectral characteristics of the small-signal surface photovoltage. The method of spectral characteristics of the low-signal surface photovoltage and the transmission method reveal information about the external quantum yield in the films studied and about the diffusion length of minority carriers in the perovskite films. As a result of this analysis, it has been established that the films obtained are naturally textured, and their bandgap is 1.59 eV. It is shown that in order to correctly determine absorption coefficient and the bandgap values, Urbach effect should be accounted for. Minority carriers' diffusion length is longer than the film thickness, which is equal to 400 nm. The films obtained are promising materials for solar cells.