10.8% efficient one-square-foot-area multifunction amorphous silicon alloy photovoltaic module

Double-junction, dual-bandgap, thin-film amorphous silicon alloy photovoltaic modules of aperture area /spl sim/900 cm/sup 2/ have been fabricated. The n, i, p layers have been deposited by conventional RF glow-discharge techniques on textured Ag/ZnO back reflectors prepared on stainless steel substrates. The bottom cell employs a graded bandgap a-SiGe alloy i-layer, and the top cell has an a-Si alloy i layer. The encapsulated monolithic modules exhibit initial aperture-area conversion efficiency as high as 10.8%, as measured under a Spire pulsed solar simulator using a peak detector circuit. The high efficiency has been obtained by: (1) improving the "tunnel" junction characteristics between the two component cells; (2) improving the uniformity; and (3) reducing module losses.<
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