PHOTOVOLTAIC PROPERTIES OF SCREEN-PRINTED CDTE/CDS SOLAR-CELLS ON INDIUM-TIN-OXIDE COATED GLASS SUBSTRATES

Screen-printed CdTe/CdS solar cells were fabricated on glass and indium-tin-oxide (ITO) coated glass substrates, and their photovoltaic and electrical properties were analyzed. The CdTe/CdS/ITO cells showed efficiencies of 8.6-8.9%, a level which is 1-4% higher than efficiencies of cells without ITO. The higher efficiencies were caused by higher fill factor (FF) values. However, the FF values of the CdTe/CdS/ITO cells are considerably lower than those expected from the relatively low sheet resistances (11-13 Omega/square)of the CdS/ITO window layers. Further, the CdTe/CdS/ITO cells showed lower open-circuit voltages and unimproved short-circuit current densities when compared with the cells without ITO. This was evident despite the high transmittances of the CdS/ITO window layers relative to those of the CdS window layers over the wavelength range from 520 to 900nm. The electrical analyses indicated that the lower photovoltaic parameters of the CdTe/CdS/ITO cells originated from a degraded junction, possibly due to the diffusion of the elements (In, O, and Sn) from the ITO layer through the CdS layer into the junction region.