Characterization of Cu2ZnSnS4 thin films deposited by one-step thermal evaporation for a third generation solar cell

Abstract

In this study, one-step thermal evaporation was employed for the fabrication of phase-pure CZTS thin films on glass substrates from single crystalline Cu-poor ingot grown by Bridgman technique. Structural analyses revealed the formation of a mono-phase CZTS kesterite structure for the thin films annealed at 450 °C under N2 atmosphere. The AFM measurements demonstrated significant morphological changes in films with increasing the annealing temperature from 200 °C to 450 °C, supporting the results obtained via XRD and Raman studies. From the optical measurements, the band gap was estimated to be 1.47 eV for the CZTS film annealed at 450 °C, which is close to the optimum value required for photovoltaic applications. As a device application of the optimized CZTS thin films, an attempt was made to construct a TiO2 NRs based and CdS-free FTO/TiO2 NRs/CZTS/Ag superstrate CZTS solar cells. TiO2 NRs were grown by hydrothermal technique, which offers a simple and a cost-effective route for large-scale production of one-dimensional nanostructures. The solar cell exhibited an open-circuit voltage of 0.35 V, a short-circuit current density of 7.28 mA/cm2, a fill factor of 23.9% and a power conversion efficiency of 0.61%, the highest efficiency recorded so far for a single-dimensional TiO2 nanostructures based superstrate CZTS solar cell.