Thin-film Sb2Se3 photovoltaics with oriented one-dimensional ribbons and benign grain boundaries

Solar cells based on inorganic absorbers, such as Si, GaAs, CdTe and Cu(In, Ga)Se-2, permit a high device efficiency and stability. The crystals' three-dimensional structure means that dangling bonds inevitably exist at the grain boundaries (GBs), which significantly degrades the device performance via recombination losses. Thus, the growth of single-crystalline materials or the passivation of defects at the GBs is required to address this problem, which introduces an added processing complexity and cost. Here we report that antimony selenide (Sb2Se3)-a simple, non-toxic and low-cost material with an optimal solar bandgap of similar to 1.1 eV-exhibits intrinsically benign GBs because of its one-dimensional crystal structure. Using a simple and fast (similar to 1 mu m min(-1)) rapid thermal evaporation process, we oriented crystal growth perpendicular to the substrate, and produced Sb2Se3 thin-film solar cells with a certified device efficiency of 5.6%. Our results suggest that the family of one-dimensional crystals, including Sb2Se3, SbSeI and Bi2S3, show promise in photovoltaic applications.