Single-step preparation and characterization of Cu ₂ZnSn(S _xSe _1-x) ₄ thin films deposited by pulsed laser deposition method

Cu ₂ZnSn(S,Se) ₄ (CZTSSe) thin films have been firstly deposited on heating quartz substrates by pulsed laser deposition (PLD) method using one-step process. The results of energy dispersive X-ray (EDX) spectroscopy show that there are some discrepancies of the elemental composition between targets and thin films. However, structural and optical properties of CZTSSe thin films show good tolerance to the composition deviation from stoichiometry. Both X-ray diffraction (XRD) and Raman spectra analysis indicate the internal compressive stress exists in CZTSSe thin films. Further transmission spectra demonstrate that the band gaps of CZTSSe thin films are higher than those of CZTSSe bulks. The internal compressive stress and the deficiency of Cu content in the films contribute to the enlargement of the band gaps of CZTSSe thin films.