Improvements in ultra-thin CdS/CdTe solar cells

Thinning the CdTe is advantageous, inter alia, to reduce the consumption of Te in solar modules; however the CdTe cell performance typically decreases with CdTe thickness. In comparison with other deposition techniques, sputtering appears to be well suited for ultra-thin device preparation partly due to control over the growth rate, grain size, and film stress. The films were magnetron sputtered on Pilkington TEC15, SnO₂:F-coated, soda-lime glass substrates with a high resistivity transparent (HRT) interfacial layer. The thickness of CdS was constant at 50-55 nm while the CdTe thicknesses ranged from 0.25 μm-2.1 μm. With optimum cell post-deposition processing, we obtained cells with efficiencies of 8.0%, 11.0%, 12.5% for CdTe thicknesses, respectively, of 0.25, 0.50, 0.75 μm. We believe that these represent the highest efficiencies yet obtained for CdS/CdTe cells with such submicron absorber-layer thicknesses.