Dependence of the Surface Morphology and Structure of CuIn0.95Ga0.05Se2 Films on the Selenization Temperature

Abstract

Depending on the choice of the technology for producing CuIn_xGa_1 – xSe₂ films, a spread in the electrophysical and photoelectric parameters of photoconverters is observed, which is primarily related to the microstructure formed in the films and their phase composition. The investigation of phase-separation processes and the formation of a single-phase CuIn_xGa_1 – xSe₂ film is a key element in fabricating high-quality absorbing layers. In the study, CuIn_0.95Ga_0.05Se₂ thin films are obtained by the two-stage selenization method of previously synthesized copper−indium−gallium layers of different thickness in the temperature range of 350°C ≤ T ≤ 550°C. The surface morphology, chemical composition, and structure of the synthesized CuIn_0.95Ga_0.05Se₂ films are investigated via scanning electron microscopy, X-ray powder diffraction, and X-ray fluorescence. It is established that the synthesized films are polycrystalline and have a developed surface with an average crystallite size of 50–140 nm. On the basis of statistical analysis of the electron-microscopy data, the lowest temperature of the onset of the selenization process and the smallest required thickness of the metal layer for the formation of a continuous thin film CuIn_0.95Ga_0.05Se₂ are determined. The obtained films can be used as the active photosensitive layer in highly efficient solar-radiation converters.