Exciton Absorption Spectrum of Thin CsPbI3 and Cs4PbI6 Films

A method for preparing thin films of CsPbI3 and Cs4PbI6 complex compounds has been developed. Their absorption spectrum is investigated in the energy range of 2-6 eV at temperatures from 90 to 500 K. It is found that the CsPbI3 compound is unstable and passes to the Cs4PbI6 phase upon heating at T >= 400 K.