Cu2ZnSn(S,Se)4 kesterite solar cell with 5.1% efficiency using spray pyrolysis of aqueous precursor solution followed by selenization

Kesterite thin film solar cell has been fabricated by chemical spray pyrolysis (CSP) of an aqueous solution followed by high temperature selenization. The pyrolysis formation of Cu2ZnSnS4 was conducted in atmospheric condition with substrate temperature of 280 °C. X-ray diffraction and Raman spectroscopy study confirmed the formation of the single phase Cu2ZnSn(S,Se)4 kesterite structure after selenization without traceable secondary phases. FESEM image shows a uniform absorber layer without carbon layer formed between CZTSSe and Mo. Power conversion efficiency of 5.1% was obtained with different amounts of selenium incorporation. Power dependent and temperature dependent photoluminescence (PL) study revealed donor-to-acceptor pairs (DAP) transition at low temperature. Severe PL quenching at temperatures above 41 K is attributed to the opening of non-radiative recombination channels from the defects associated with non-stoichiometric elemental ratio. Therefore, further enhancement of power conversion efficiency can be achieved by better control of stoichiometry.