Solar cells of indium tin oxide on silicon

Solar cells consisting of heterojunctions between p-silicon wafers and transparent indium tin oxide (ITO) have been fabricated and characterized. The motivation for such cells was to investigate inexpensive, low temperature processing techniques not involving diffusion. The new advances are: (1) the successful use of a solar cell front layer of nearly transparent, but highly conductive ITO and (2) the incorporation of ion-beam sputtering in the fabrication process. The cells are fabricated by placing oxidized silicon wafers in a 4-inch ion beam. The silicon dioxide is sputter etched and 2000 Å of ITO are deposited during the same pumpdown. This technique yields as-sputtered films of r-cm resistivity and light transmissivity above 80 percent over the visible spectrum. The finished cells have an open circuit voltage of 0.45 volts and a short circuit current of 12.5 ma/cm². The curve fill factor is 0.6. This yields a maximum output of 3.4 mw/cm²and an efficiency of 3.3%.