Effect of selenium incorporation at precursor stage on growth and properties of Cu2ZnSnSe4 thin films

In the present work, the effect of the selenium incorporation in between the Sn-ZnSe-Cu precursor layers on growth of Cu2ZnSnSe4 thin films by employing selenization is reported. Multiple stacks of precursors (Sn/Se/ZnSe/Se/Cu/Se) were sequentially evaporated in high vacuum onto soda lime glass substrates held at 100 °C and their subsequent selenization at 350 °C using a tubular furnace led to the complete crystallization into single phase Cu2ZnSnSe4 films. X-ray diffraction pattern of stacked layers selenized at 350 °C revealed the formation of kesterite-type Cu2ZnSnSe4 films with a preferred orientation along (112) plane. Raman analysis using multi wavelength excitation confirms the growth of single phase CZTSe films. Secondary ion mass spectroscopy (SIMS) depth profiles illustrated fairly uniform distribution of constituent elements. Optical absorption studies of the films showed an optical band gap of 0.97 eV with high absorption coefficient (>104cm−1). The electrical properties of the films exhibited p-type conductivity with resistivity of 4.18 Ωcm, mobility of 11.3 cm2(Vs)−1 and carrier concentration of 1.32 × 1017 cm−3. Our approach and results would open a new way for the synthesis of Cu2ZnSnSe4 directly on plastic substrates.