Current Enhancement via a TiO2 Window Layer for CSS Sb2Se3 Solar Cells: Performance Limits and High VOC

Antimony selenide (Sb2Se3) is an emerging chalco-genide photovoltaic absorber material that has been the subject of increasing interest in recent years, demonstrating rapid efficiency increases with a material that is simple, abundant, and stable. This paper examines the material from both a theoretical and practical standpoint. The theoretical viability of Sb2Se3 as a solar photovoltaic material is assessed and the maximum spectroscopically limited performance is estimated, with a 200 nm film expected to be capable of achieving a photon conversion efficiency of up to 28.2%. By adapting an existing CdTe close-spaced sublimation (CSS) process, Sb2Se3 material with large rhubarb-like grains is produced and solar cells are fabricated. We show that the established CdS window layer is unsuitable for use with CSS, due to intermixing during higher temperature processing. Substituting CdS with the more stable TiO2, a power conversion efficiency of 5.5% and an open-circuit voltage V-oc of 0.45 V are achieved; the voltage exceeding current champion devices. This paper demonstrates the potential of CSS for scalable Sb2Se3 deposition and highlights the promise of Sb2Se3 as an abundant and low-toxicity material for solar applications.