Nonmonotonic temperature-dependent bandgap change of CsPbCl3 films induced by optical phonon scattering

The CsPbCl 3 perovskite films are successfully grown on quartz substrates by radio frequency (RF)-magnetron sputtering method and their detailed photoluminescence properties are studied over the temperatures from 10 K to 300 K. There exists one near bandgap emission peak (∼410 nm) in the violet region with typical lifetime of few nanoseconds at room temperature . To our surprise, with temperature increasing, this band shows nonmonotonic shift, which is different to the traditional semiconductor like silicon or the same group of perovskites like MAPbI 3 or CsPbBr 3 . The origin of this band and its temperature-dependent shift can be well described with the Bose-Einstein two-oscillator model that takes into account the interaction between electrons and phonons including acoustic phonons and optical phonons. Due to the anisotropic optical properties of the perovskite crystal, the (001)-orientated films have stronger electron phonon coupling and weaker exciton binding energy.