Shining Light on Sulfide Perovskites: LaYS₃ Material Properties and Solar Cells

The sulfide perovskite LaYS₃ has been recently identified as a promising wide band gap photoabsorber material by computational screening techniques. In this study, we combine experiment and theory to comprehensively characterize LaYS₃ thin films produced by sulfurization of sputter-deposited precursors. An attractive feature of LaYS₃ is its optimal band gap (2.0 eV) for application as a wide band gap photoabsorber in tandem solar energy conversion devices. Promisingly, the LaYS₃ films are photoconductive, with a grain size in excess of 1 μm and comparable recombination time scales to state-of-the-art hybrid halide perovskite absorbers. Although the fabrication of solar cells based on LaYS₃ absorbers is complicated by the high temperature necessary to grow the compound, complete solar cells could be produced in this work by growing LaYS₃ on refractory metal back contacts. These are the first reported solar cells based on a sulfide perovskite absorber. A major reason for their poor performance could be the highly localized trap states observed directly by photoluminescence imaging of LaYS₃, which may also explain the surprisingly long carrier lifetimes and the low carrier mobility found in this material