Structural, optical and electrical properties of Cu2CoSnS4 thin film solar cells prepared by facile sol-gel route

Abstract

• Copper cobalt tin sulfide (Cu 2 CoSnS 4 ) thin films were deposited by sol-gel method. • Physical and chemical properties of Cu 2 CoSnS 4 thin film were investigated. • The Cu 2 CoSnS 4 –based solar cells with an efficiency of 4.83% were achieved. The copper cobalt tin sulfide Cu 2 CoSnS 4 (CCTS) thin films are among the most promising materials for power conversion. We carried out a study on copper-cobalt tin sulfide thin films deposited via a simple route using the sol-gel spin-coating method. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive analysis, and Hall effect measurements were performed to investigate the impact of the annealing temperature on structural, morphological, compositional, optical, and electrical properties of the CCTS thin films. The optimum annealing conditions for obtaining pure CCTS thin films, with good crystallinity, stoichiometry, and surface morphology were found to be 300 °C for 60 min in a nitrogen atmosphere. In addition, the films show a p-type conductivity with a sheet carrier concentration of 1.2 10 17 cm −3 , sheet resistivity of 0.18 Ω.cm, Hall mobility of 5.8 cm 2 /V.s, the optical band gap of 1.4 eV and an absorption coefficient more than 10 4 cm −1 . In addition, the CCTS-based solar cells were fabricated. Under simulated AM 1.5 illumination conditions, the solar cells showed a high open-circuit voltage of 0.79 V, a short-circuit current density of 17.5 mA/cm 2 , a fill factor of 35%, and the conversion efficiency of 4.83 %. These results indicate that the annealed CCTS thin films at 300 °C in nitrogen atmosphere without sulfurization process are promising for low-cost effective thin-film solar cells.