Colossal Broad Band Antireflection from Conformally Grown Cu₂O on Pyramidally Textured Si and its Photovoltaic Applications

In this paper, we show the efficacy of a conformally grown, self‐organized Cu₂O overlayer on chemically synthesized, pyramidally textured silicon substrate for a colossal suppression of optical reflection loss. In particular, we demonstrate that p‐Cu₂O film deposited on a chemically textured n‐Si substrate shows an ultra‐low average surface reflectance (≈0.25%) over the entire spectral range (300–2400 nm), whereas the same turns out to be ≈25% for the film deposited on an as‐obtained n‐type Si substrate. It is observed that in the former case, Cu₂O grows in the form of leaf‐like nanostructures, which is attributed to be responsible for such a low reflectance. In addition, under both configurations, the p‐Cu₂O/n‐Si heterostructure shows a non‐linear current–voltage characteristics, clearly suggesting the formation of barrier junctions. Further, it is found that a solar cell fabricated with p‐Cu₂O overlayer grown on a pyramidally textured n‐Si substrate shows an eight times higher efficiency compared to the one grown on an as‐obtained n‐Si substrate. This study will pave the way to design cost‐effective and efficient copper oxide‐based solar cells.