Synthesis of Cu2ZnSnS4 films from co-electrodeposited Cu-Zn-Sn precursors and their microstructural and optical properties

The Cu2ZnSnS4 (CZTS) films were successfully prepared using a process of co-electro-deposition of Cu-Sn-Zn precursors by a novel electrolyte formula and optimized parameters on Mo substrates, succeeded by annealing in saturated sulfur atmosphere. The optimized electrolyte formula was achieved as 0.16 M CuSO4 center dot 5H(2)O, 0.33 M ZnSO4, 0.08 M SnCl2 center dot 2H(2)O, 2.25 M NaOH, 1.36 M C6H5Na3O7 and 1.00 M C4H6O6 under a voltage of -1.62 V for 5 min. Cu3Sn, Cu6Sn5 and Cu4Zn alloys were firstly synthesized at temperature lower than 300 degrees C. At 300 degrees C, these alloys decomposed in sulfur atmosphere and CuS, SnS and ZnS binary phases were formed. Ternary Cu4SnS6 formed through reaction between CuS and SnS above 350 degrees C. Finally, the CZTS films were synthesized through reaction among CuS, SnS, ZnS and Cu4SnS6 sulfides. CZTS films synthesized at 550 degrees C for 1 h had an average atomic ratio of 0.96 and 1.1 for Cu/(Zn + Sn) and Zn/Sn, respectively. The photoluminescence peaking at about 1.55 eV in the prepared samples demonstrated a high quality of the CZTS film. (C) 2013 Elsevier B.V. All rights reserved.