Improving the light trapping ability and flexural strength of ultrathin monocrystalline silicon wafers with submicron pyramid textures

Ultrathin monocrystalline silicon (mono-Si) wafers with thicknesses less than 100 μm have gained significant attention from the PV community, not only because of the decreased consumption of silicon materials but also because of their excellent flexural strength. However, the 1–3 μm pyramids introduced by the conventional alkaline texturing process affect the mechanical strength of ultrathin wafers. In this study, we demonstrate a novel texturing process that combines metal-catalyzed chemical etching and alkaline etching for ∼80 μm wafers. The resulting submicron pyramids of ∼865 nm endowed the wafers with better light trapping ability and flexural strength than did conventional alkaline-textured wafers with the same thickness. Due to the introduction of a porous silicon layer, submicron pyramids can form very quickly in 240 s at 60 °C; as a comparison, the conventional alkaline texturing process should be carried out in 420 s at 80 °C. The flexural strength of textured ultrathin wafers can be largely enhanced by using a separate edge rounding procedure. Therefore, such a novel texturing process combined with a simple edge rounding procedure offers a promising solution for texturing ultrathin wafers as a footstone for fabricating flexible mono-Si solar cells.