Investigation of Optical and Dielectric Constants of Organic-Inorganic CH3NH3PbI3 Perovskite Thin Films

Abstract

CH 3 NH 3 PbI 3 thin films with thicknesses in the region of 230-365 nm were prepared. The films were characterized by scanning electron microscope (SEM), x-ray diffraction (XRD), ultraviolet-visible (UV-Vis) absorption and transmittance spectra. Based on the Kramers-Kronig relation and the transmittance spectra, the optical and dielectric constants of the CH 3 NH 3 PbI 3 thin films were investigated. Our results show that the absorption coefficient, extinction coefficient, refractive indices, real and imaginary components of the dielectric constant of the CH 3 NH 3 PbI 3 films are basically independent on the thicknesses of the films, which indicate our results are reliable. At 500 nm, above parameters of the films are ~ 1.38x10 5 cm-1 , 0.55, 2.70, 7.01, and 3.13, respectively. The band gap is 1.595 eV. The refractive index of CH 3 NH 3 PbI 3 thin films is 2.84 at 633 nm, which imply that CH 3 NH 3 PbI 3-based solar cells (SCs) are ideal antireflection coatings for silicon SCs and are applicable to be top SC in monolithic silicon-based tandem SCs for beyond the efficiency limit of Si SCs. Our results are meaningful for designing optoelectronic devices related to the perovskite thin-films.