Synthesis and characterization of Cu₂ZnSnS₄ thin films by the sulfurization of co-electrodeposited Cu-Zn-Sn-S precursor layers for solar cell applications

Cu₂ZnSnS₄ (CZTS) absorbers have been successfully deposited on tin-doped indium oxide coated glass (ITO/glass) substrates by sulfurization process of co-electrodeposited Cu-Zn-Sn-S precursor thin films at various annealing temperatures ranging from 500 to 580 °C for 30 min in an atmosphere of Ar-H₂S (6.5%). The effects of sulfurization temperature on the structure, morphology, composition and optical properties of CZTS thin films have been investigated in details. XRD and Raman measurements reveal that the intensity of preferential orientation along the (112) direction becomes relatively more intense and sharp with increasing annealing temperature. The morphological and chemical composition studies indicate the formation of compact and homogenous CZTS thin films with Cu-poor and Zn-rich composition at a sulfurization temperature of 560 °C. And its band gap energy is around 1.50 eV. The AZO/i-ZnO/CdS/CZTS/ITO/glass thin-film solar cell is fabricated with the CZTS absorber layer grown at an optimized sulfurization temperature of 560 °C. It shows a power conversion efficiency of 1.98% for a 0.25 cm ² area with V_oc = 490 mV, J_sc = 9.69 mA cm ^-2 and FF = 40.03%.