Earth Abundant Cu₂FeSnS₄ Thin Film Solar Cells

Abstract

Firstly, copper iron tin sulfide Cu 2 FeSnS 4 (CFTS), thin films are fabricated by the sol-gel method on soda lime glass and FTO substrates at relatively low temperature without sulfurization step. The structural, morphological, compositional and optical properties of synthesized CFTS thin films have been studied by X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and UV- visible - NIR spectrophotometer respectively. Secondly, the CFTS-based solar cells with structure Au / p-CFTS / n-CdS / i-ZnO / FTO has been fabricated and characterized under AM 1.5 standard illumination conditions. XRD and Raman spectroscopy revealed that the formation of a pure phase of CFTS thin film with an average crystallites size of 60 nm. SEM analysis showed a compact and uniform CFTS thin film. EDS analysis confirmed the presence of Cu, Fe, Sn and S with a stoichiometry 2:1:1:4. The optical band gap was found to be 1.5 eV. The best CFTS based solar cell showed a short-circuit current density of 12.16 mA.cm ⁻² , an open-circuit voltage of 0.78 V, a Fill factor of 50 % and an efficiency of 4.7%.