deposition and characterization of wide band gap CuGaSe2 thin films and solar cells

CuGaSe₂ absorber layers were grown by evaporating elemental Cu, Ga and Se on molybdenum coated soda lime glass substrates using three-stage process with substrate temperature monitoring. The grain size of the films decreased with the increase of Ga composition, but the morphology of the films improved. The optical band gap of the absorbers is around 1.68 eV regardless of Ga concentration. Using these films the solar cells with a structure SLG/Mo/CuGaSe₂/CdS/ZnO/AI were fabricated. Current-voltage characteristics and spectral response measurements were performed to evaluate device parameters and to analyze loss factors. In optimal condition, the absorber film is 1.9 μm thick and slightly Ga rich bulk composition [Cu]/[Ga] =0.88 and we obtained V_OC = 0.81 V, J_SC = 11.9 mA, ff =0.635 and η = 6.1 %.