Study and characterization of γ-ray doses dependent properties of CuPbI3 perovskite thin films

The impact of γ-ray on the halide perovskite (CuPbI3) thin film has been investigated in this work. Nanocrystalline and homogeneous CuPbI3 material was effectively deposited on a glass substrate using spin coating method. The thin film, which has a thickness of approximately 227 nm, was exposed to γ-ray's source (Co60 with a dose rate of 7.328 kGy/h) in the range of 0–75 kGy. Then the structural, morphological, electrical and optical properties of CuPbI3 thin films were studied before and after being irradiated. X-ray diffraction (XRD) analysis confirmed the hexagonal phase structure, and the crystalline size decreased from 42 to 16 nm with increasing crystallinity up to 50 kGy. Field emission scanning electron microscopy (FESEM) revealed that the grain size (33-23 nm) and surface of thin films were significantly affected by γ-ray's doses variation. The optical transmission and reflectance of CuPbI3 thin films were studied by means of their response to incident γ-rays. The estimated band gap (Eg) slightly increased from 2.23 to 2.3 eV with increasing γ-rays dose from 0 to 50 kGy and then deceased afterward. Other optical parameters, such as Urbach energy, extinction coefficients, refractive index, optical density and dielectric constants, were determined before and after γ-ray's exposure. Photoluminescence (PL) spectra depict the transition peak at 620.35 nm and the structural defect peak at 606.3 nm. The intensity of the PL peaks could depend on the γ-rays dose with respect to the as-deposited thin films. Impedance spectroscopy of all samples revealed that the grain boundary resistance gradually reduced with increasing γ-ray's dose. This study concludes that the incident γ-rays play a main role in properties of the CuPbI3 thin film, which is favorable for sensing/detecting applications of γ-ray's.