Synthesis of Cu₂ZnSnS₄ (CZTS) absorber by rapid thermal processing (RTP) sulfurization of stacked metallic precursor films for solar cell applications

Cu₂ZnSnS₄ (CZTS) absorbers have been grown on Mo-coated glass substrates by the rapid thermal processing (RTP) sulfurization of stacked metallic precursor (CZT) films at different annealing temperatures ranging from 500 to 580 C for 5 min in sulfur atmosphere. The effects of sulfurization temperature on the structural, morphological, chemical, and optical properties of the CZTS absorbers have been investigated. XRD and Raman studies reveal that the as-deposited stacked metallic precursor films consist of metal elements such as Zn, Sn and binary alloys such as Cu₆Sn ₅, Cu₃Sn and CuZn. The sulfurized CZTS absorber films have single phase polycrystalline kesterite crystal structure with dense morphology. At 580 C, the CZT metallic precursor film is fully sulfurized with Zn-rich and Sn-poor composition, and its bandgap energy is found to be 1.50 eV. The solar cell fabricated with the CZTS absorber grown at an optimized sulfurization temperature of 580 C shows a conversion efficiency of ~5% for a 0.44 cm ² area with V_oc=561 mV, J_sc=18.4 mA/cm ², and FF=48.2.