We have deposited textured ZnO:Al films over large areas using a reactive-environment hollow cathode sputtering (RE-HCS)
system developed in house, and have achieved excellent carrier mobilities (up to 49.5 cm2/Vs at a carrier
concentration of 4.42 x 1020/cm3). Both the electrical properties and optical properties (total transmission and haze) are
superior to those exhibited by commercially available SnO2:F. Using these textured ZnO:Al films, we have achieved an
a-Si:H solar cell efficiency boost of 8% relative to commercial SnO2:F superstrates which resulted from improvements
in all three PV parameters, namely Voc, Jsc, and FF. We have also determined the dependence of cell performance on the
degree of haze in the ZnO:Al films. Electrical, physical, and optical properties of ZnO:Al and SnO2:F, as determined by
four-point probe, Hall effect, SEM, AFM, ICP, transmission (total and diffuse), and work function measurements are
presented and correlated to the observed differences in a-Si solar cell performance. We have also developed a refractive
index matching layer that, when inserted between the TCO and the a-Si:H layers, resulted in an increase in Jsc of 3%.
Finally, we present some experiments on the effect of TCO type on nc-Si:H solar cell performance. From these
experiments, we confirmed that SnO2:F by itself is not a suitable TCO for nc-Si:H cells, but found that SnO2:F
overcoated with TiO2 followed by ZnO was the most effective superstrate for this type of cell.