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

Double-junction, dual-bandgap, thin-film amorphous silicon photovoltaic modules of aperture area ) 900 cm super(2) have been fabricated. The n, i,p layers been deposited by conventional rf glow-discharge technique on textured Ag/ZnO back reflectors prepared in 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.