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

• Single phase Cu2ZnSnS4 is synthesized by rapid thermal processing sulfurization.
• Higher annealing temperature improves the crystallinity of Cu2ZnSnS4 absorber.
• Cu2ZnSnS4 absorber is fully sulfurized at 580 °C.
• A solar cell with a ~5% conversion efficiency is demonstrated.

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 Cu6Sn5, 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 cm2 area with Voc=561 mV, Jsc=18.4 mA/cm2, and FF=48.2.