Light management on industrial size c-Si solar cells by Si nanowires fabricated by metal-assisted etching

Abstract

Absorption of the light by a solar cell can be improved significantly by light trapping structures formed on the front surface of the device. In particular, thin crystalline and amorphous solar cells are expected to benefit from the improved light absorption in a region closer to the surface of the cell. Recently, we have shown that vertically aligned silicon (Si) nanowires formed on flat (100) Si wafer surface by metal assisted etching can effectively be used for this purpose. In this paper we present demonstration of nanowire application to industrial size solar cell system and a comparison between flat and pyramid textured Si wafers. Standard procedures were followed to fabricate solar cells with and without Si nanowire process on mirror like and pyramid textured Si wafers. The dependence of the solar cell parameters on the process parameters was studied systematically. Reflection spectra showed successful light trapping behavior on the surface of the cells. In all samples, we have obtained excellent current-voltage (I-V) characteristics with high fill factors. However, the efficiency of the cells was found to decrease with the etch duration. This can be attributed to the increased recombination along the nanowires or increased surface area due to the roughening of the surface after etching process.