Preparation of Cu2ZnSnS4 Solar Cells by Sputtering Three Sulfide Targets at Different Sulfurization Annealing Temperatures

Cu2ZnSnS4 (CZTS) thin films were prepared by sputtering three sulfide targets at different sulfurization annealing temperatures from 550 to 600 ℃. The morphology, microstructure and optical-electrical properties of CZTS thin films were investigated. It was found that the crystal quality at the CZTS/Mo interface without intermediate layers was promising and the thickness of MoS2 was limited to within 90 nm. The expected results were achieved after 575 ℃ sulfurization annealing, indicating that sputtering three sulfide targets can compensate for part of the sulfur partial pressure in the sulfurization process. The measurements showed that CZTS thin film (called S2) sulfurized at 575 ℃ with a mobility of 282.7 cm2/V·s and a band gap of 1.49 eV had the best electrical and optical properties. The elemental depth profile showed that the composition in S2 was homogeneously distributed. Finally, the CZTS solar cell with an active area 0.8 cm2 was successfully fabricated and the conversion efficiency was 2.7%. The max external quantum efficiency exhibited a value of 79.7%. The short-circuit current density and open-circuit voltage of the device were 20.12 mA/cm2 and 381 mV, respectively. The relationship between the composition and the voltage deficit was also discussed.