Abstract
Spray technique is used for the deposition of Cu2ZnSnS4 (CZTS) films, taking the chlorides of Cu(I), Zn and Sn(II) along with thiourea as precursors for the spray solution, with the substrate temperature varying from 200 degrees C to 450 degrees C. Use of these precursors results in CZTS phase formation starting at 200 degrees C and only beyond 350 degrees C the secondary phases are formed. CZTS films deposited at 200 degrees C and 250 degrees C show high resistivity's of 502.39 Omega-cm and 51.84 Omega-cm, respectively and carrier concentrations of 2.85 x 10(14) cm(-3) and 5.55 x 10(15) cm(-3), respectively. The formation of secondary phases at 400 degrees C and 450 degrees C strongly affects the film properties. CZTS films deposited at 350 degrees C show the best resistivity of 0.19 Omega-cm. SEM analysis shows growth of nano-flakes on the surface of the film deposited at 350 degrees C, and C-AFM reveals that the film has the highest current range due to high internal conductivity which can be the cause of reduced film resistivity and enhanced optical absorption. CZTS film at 350 degrees C had the lowest activation energy calculated from the Arrhenius plot of In sigma vs 1000/T. Energy dispersive spectroscopy (EDS) analysis shows that the atomic percentages of the constituents in the CZTS films change with the temperature and accordingly affect the band gap. The film deposited at 350 degrees C is nearly stoichiometric with the band gap of 1.45 eV making it best suited for solar cell fabrication. (C) 2015 Elsevier Ltd. All rights reserved.