Optoelectronic properties of R-F magnetron sputtered Cadmium Tin Oxide (Cd₂SnO₄) thin films for CdS/CdTe thin film solar cell applications

The influence of substrate temperature on the microstructural behavior, optical, electrical properties and on the scattering mechanism of charge carriers were studied for the as-prepared radio-frequency (R-F) magnetron sputtered Cadmium Tin Oxide (Cd₂SnO₄) thin films. Films prepared at the substrate temperature of 300 °C were found to be polycrystalline in nature with preferential orientation along (3 1 1) plane. Well pronounced Moss-Burstein shift, in the transmittance spectra with dispersions in the optical band gap from 3.07 to 3.30 eV, was observed at substrate temperatures between 25 and 300 °C. Optical property of high visible transmittance was retained by the films. Analysis of the electrical properties on the prepared crystalline Cd₂SnO₄ films showed a calculated resistivity of 10^-3-10^-4 Ω cm, with n-type carrier density in the range of 10¹⁹-10²⁰ cm^-3 and the charge carrier mobility in the range of 63-30 cm²/V s. The effects of structural, compositional and optical properties on the scattering mechanism of charge carrier are elaborated and reported to be an experimental evidence for the theoretical predictions. The results revealed the essential DC electrical conduction behavior, which is ideal for the fabrication of Cd₂SnO₄-based CdS/CdTe thin film solar cells.