Understanding light absorption realized among nanopillar-structured Sb ₂ S ₃ thin-film solar cells for seeking high performance

Because of the quasi-1D crystal structure, antimony sulfide (<i>S</i><i>b</i>₂<i>S</i>₃) exhibits low symmetry and complex deep defects, which result in a relatively inefficient carrier collection and slow progress in efficiency improvements. Introducing nanostructures into <i>S</i><i>b</i>₂<i>S</i>₃ thin-film technology may be a useful method to decouple the light absorption path and carrier collection path, allowing the use of a very thin light absorption layer, which can boost more efficient carrier collection. In this work, the light absorption behaviors among the nanopillar-structured <i>S</i><i>b</i>₂<i>S</i>₃ units have been studied by carrying out finite element simulations constructed on the Mo-coated or uncoated glass substrates. When the length of the nanopillar is large enough, or the radius is small enough, making the nanopillar more like a slim nanowire, the in-coupling mode usually works positively on the absorption enhancement, especially during the long-wavelength range. Additionally, a very high density of nanopillar units usually boosts light scattering absorption. These results provide a practical guide to design and fabricate nano-structured <i>S</i><i>b</i>₂<i>S</i>₃ thin-film solar cells by using very thin light-absorption layers, thus efficiently enhancing carrier collection for high performance.