Performance of solar cells fabricated on black multicrystalline Si by nanowire decoration

Abstract

Vertically aligned Si nanowire (NW) arrays fabricated by metal-assisted etching technique were applied to industrial sized (156mm×156mm) multicrystalline Si cells as an anti-reflective (AR) medium. The NW lengths (between 0.15 and 2.2μm) were controlled by etch duration from 5 to 50min. A completely black surface could be observed, demonstrating excellent AR properties in the entire range of the solar spectrum, even without additional anti-reflective coating layer (e.g., SiNx:H). Standard Si solar cell fabrication protocols were followed for both samples with NW arrays and to reference samples textured in standard stain etch solution. Cell parameters have been studied as a function of NW length. Results show that Si NW arrays can be used on multicrystalline Si solar cells as an AR coating. Without applying a superior passivation technique, cell conversion efficiencies are observed to normally degrade with increasing lengths of NW's, such that the highest efficiency in NW samples was resulted from the shortest NW's. It is clear that an effective passivation eliminating recombination along the NW's and optimized doping could further improve the performance of the cell. Structuring the surface of the multi-crystalline wafers with metal assisted etching is shown to be a promising alternative to presently used acid-based texturing processes.