Cu2SnS3-based thin film solar cell from electrodeposition-annealing route

Cu2SnS3 is a new emerging material for thin film photovoltaics, composed of three abundant and non toxic elements. Its p-type conductivity, bandgap of 0.93 eV and absorption coefficient above 104 cm-1 make it a promising absorber layer for p-n heterojunction devices. In this study, the Cu2SnS3 absorber is synthesized from electroplated stacked Cu-Sn precursors further annealed in chalcogen atmosphere (S and SnS). The electroplating has been processed on upscaled 45 x 50 mm2 Mo-coated soda-lime glass substrates on which the metallic layers seem to delaminate easily from the substrate due to increased stress between them. To reduce this stress the precursors are subjected to pre-alloying treatments. The effects of pre-alloying are investigated in terms of final absorber morphology, composition and crystal structure. Precursors are annealed at 250°C and 350°C. The prealloying at 350°C is far above the melting point of Sn around 230°C and these samples show de-wetting. The as-deposited and 250°C pre-alloyed samples are processed further into absorber layers and solar cells. The finished absorber layers show mainly monoclinic Cu2SnS3. Absorbers completed into devices show a device power conversion efficiency of 0.64%. The spectral response suggests the existence of two bandgaps, consistent with previous results.