Experimental study of the optical properties of Cu2ZnSnS4 thin film absorber layer for solar cell application

Abstract

Cu2ZnSnS4 (CZTS) has become the subject of considerable interest due to its use as thin film solar cell material. Current thin film solar technologies based on CuInxGa1-xSe2 (CIGS) and CdTe photo-absorber materials use rare and expensive elements, such as In, Te, Ga and toxic Cd which severely limit the mass productions and deployment of solar cells. CZTS is an intrinsically p-type material with a large optical absorption coefficient (α = 104 cm-1) and exhibits a tunable direct optical band gap in the range between 1.49 to1.51 eV. The CZTS thin films were deposited on soda lime glass by dip coating method with sulfurized Cu, Zn, Sn precursors and were characterized CZTS thin film as absorber layer of solar cell. The optical characterization has been performed by UV-Vis spectrometry in order to study the effect of Cu/(Zn + Sn) ratio on the absorption coefficient and the band gap energy of the prepared thin films. As the ratio is increased (0.4 to 0.7), the absorption coefficient increases slightly whereas the band gap energy decreases.