Comparative Study of Cu2ZnSnS4 Thin Films Prepared by Chalcogenide and Single Targets

Abstract

To verify feasibility and superiority of preparing Cu2ZnSnS4 (CZTS) thin films and solar cells by sputtering chalcogenide targets instead of single targets, two kinds of CZTS thin films were synthesized via multi-period sputtering ZnS-Sn-CuS and Zn-Sn-Cu, respectively. Influence of different sputtering targets on crystal structure, phase purity, surface roughness, chemical composition, surface and cross-sectional morphology, and optical-electrical properties of CZTS thin films were investigated in detail. Subsequently, the complete devices were fabricated according to SLG/Mo/CZTS/CdS/i-ZnO/ZnO:Al/Ni-Al and J-V characteristics of cells were measured. The results show that the solar cell made of ZnS-Sn-CuS precursor owns an open-circuit voltage of 611 mV, short-circuit current density of 21.28 mA/cm2 and efficiency of 5.11% while the solar cell based on single targets shows an open-circuit voltage of 594 mV, short-circuit current density of 18.56 mA/cm2 and an efficiency of 4.13%. It is attributed to the fact that the CZTS thin films prepared by ZnS-Sn-CuS have smoother, denser surface and better longitudinal growth compared with those prepared by single targets. The result confirms the superiority of the CZTS thin film and solar cells prepared using the chalcogenide targets over those from single targets.