Effects of sulfurization temperature on phases and opto-electrical properties of Cu₂ZnSnS₄ films prepared by sol–gel deposition

Cu₂ZnSnS₄ (CZTS) thin films were prepared by sol–gel method and sulfurization process. The effects of the sulfurization temperature on the structural, morphological, compositional, and opto-electrical properties of the CZTS films were investigated. X-ray diffraction and Raman spectroscopy analyses confirmed the formation of CZTS films. With increasing sulfurization temperature, the crystallinity of the films was enhanced, which was accompanied by metallic deficiency, especially tin loss. When the sulfurization temperature was increased from 460 to 540 °C, the optical band-gap value decreased from 1.63 to 1.38 eV, while the resistivity and mobility increased from 1.415 to 1313 Ω·cm and from 0.372 to 7.231 cm²/V·s, respectively. The best CZTS film properties with a bandgap of 1.47 eV, resistivity of 581.5 Ω·cm, carrier concentration of 2.165 × 10¹⁶ cm⁻³ and mobility of 1.411 cm²/(V·s) were achieved at a sulfurization temperature of 500 °C, and make the films suitable as absorbers for solar cells. - Highlights: • The Cu₂ZnSnS₄ (CZTS) films were prepared by sol–gel method following sulfurization. • The sulfurization temperature has the effects on the electrical properties. • The tin loss is increased with the increasing sulfurization temperature. • The secondary phases like ZnS make the electrical properties worse. • The CZTS films sulfurized at 500 °C have the best opto-electrical characteristics