Two step growth mechanism of Cu2ZnSnS4 thin films

Cu2ZnSnS4 (CZTS) semiconductor is rapidly emerging as the best absorber layer for next generation solar photovoltaics. Its cost effectiveness, environment-friendly nature, wide presence of chemical constituents in nature and high absorption coefficient with suitable energy band gap for effective utilization of solar spectrum makes it a viable alternative. The present work summarizes the preparation of CZTS films through a two-step process consisting of co-sputtered metallic precursors on glass substrates kept at 230 degrees C Followed by sulfurization for 2 h in the ambience of elemental sulfur vapor at different temperatures ranging from 300 to 550 degrees C. The X-ray diffraction (XRD) and Raman analysis make it explicit that the sulfurization temperature has significant impact on reaction mechanism resulting in various hi-metallic, mono and binary metal sulfides. The diffraction pattern noticed at 500 degrees C corresponding to (112), (220) and (312) planes confirms the single phase CZTS as evidenced by weak and strong Raman modes at 285, 337 and 352 cm(-1), The transmittance and reflectance measurements of optimized CZTS films revealed that the films have an energy band gap of similar to 1.56 eV. The optimized films were characterized by scanning electron microscopy (SEM) attached with EDS to know the morphological features and elemental quantification. The single phase CZTS films have exhibited p-type conductivity with sheet resistance similar to 6.8 x 10(3) Omega/sq., carrier concentration similar to 9.1 x 10(17) cm(-3) and hole mobility similar to 16.6 cm(2)V(-1) s(-1)