ELECTROCHEMICAL CODEPOSITION OF INDIUM AND GALLIUM FOR CHALCOPYRITE SOLAR-CELLS

Thin Cu/In/Ga films were prepared by electrochemical codeposition of i ndium and gallium from an aqueous cyanide bath. Sputtered copper layer s with a small gallium content (Cu0.86Ga0.14) on Mo/soda-lime glass se rved as a substrate. A change of the indium to gallium ratio in the fi lms was achieved by applying different deposition potentials. Variatio n of the film morphology was observed with different contents of the t wo elements (In, Ga). The Cu/In/Ga layers were characterized by X-ray diffraction, scanning electron microscopy-energy dispersive X-ray anal ysis and Auger electron spectroscopy. The precursor layers were reacti vely annealed in selenium vapour at temperatures above 500 degrees C t o form Cu(In, Ga)Se-2 semiconducting chalcopyrite layers. Followed by a CdS buffer layer and a ZnO layer as the transparent conducting oxide the Glass/Mo/Cu(In, Ga) Se-2/CdS/ZnO solar cell structure was complet ed. An efficiency eta = 6.6% with an open circuit voltage U-OC = 413 m V, a short current density I-SC = 32.5 mA cm(-2) and a fill factor FF = 0.49 was achieved. The obtained results prove that the electrochemic al In/Ga codeposition from an aqueous bath can contribute to the thin film processing of chalcopyrite solar cells.