Characterization of Na-doped Cu2ZnSnS4 thin films and electrical analysis of Al/ p-Cu2ZnSnS4: Na (1%)/Mo structure

Abstract

The present work deals with the study of the microstructure, morphology and optical properties of vacuum annealed Cu₂ZnSnS₄: Na films deposited on heated glass substrates by single source vacuum thermal evaporation. X-ray diffraction and Raman spectroscopy characterized the structure of the samples and showed that they are all polycrystalline with kesterite phase and a preferred (112) plan orientation. Sodium doping reduces the FWHM, increases grain size and a decrease in stress and dislocations. AFM and SEM studies of sodium-doped Cu₂ZnSnS₄ thin films, known as CZTS, indicate they have a fairly smooth surface and that the morphology improves with Na doping. A good crystallinity, with average transmittance above 85%, was obtained for the thin films doped with 1% sodium. A decrease in the Eg band gap value towards optimum values with Na incorporation compared to the undoped sample. The Na dopant enhances the Hall effect characteristics by increasing the carrier concentration and reducing the resistivity. These properties make CZTS: Na 1% a suitable material for many applications such Schottky diode… Therefore, a Schottky diode was designed and realized by Al contact on CZTS: Na 1%/Mo. Electrical characteristics based on current–voltage were determined. The analysis is based on the theory of thermionic emission, which allows the determination of the saturation current, the ideality factor, the series resistance and the barrier height, which were estimated to be 1.19 × 10⁻⁴A, 1.57, 0.54 eV and 10.78Ω, respectively.