Photoresponse properties and energy gap of CsPbBr₃–CsPb₂Br₅ compound thin film prepared by one-step thermal evaporation method

We proposed the preparation of the compound thin film of CsPb₂Br₅ and CsPbBr₃ perovskites via thermal evaporation method with post-annealing. The optical absorption, energy gap, and photoresponse properties of the compound thin films were investigated. Over 90% transmittance in visible region of 550–700 nm was obtained, and the energy gap of thin film was found to be in the range of 2.28–2.35 eV. Using 405 nm laser, the compound thin film showed obvious response dependence on light power. Even if the large conductive channel of 1 mm × 100 μm was used, thin film possessed still good cycle characteristics, available responsivity, and a rapid response at applying 5 V.