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 mu m 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.