Wide Bandgap Tellurium Oxide Semiconductor as A Back Contact Modifier for Efficient n-i-p Sb2Se3 Solar Cells

The wide-bandgap and p-type semiconductor layer plays a crucial role in the antimony selenide (Sb2Se3) solar cells, as it can provide carrier confinement and inhibit interface recombination. In this work, the tellurium (Te) thin layer is innovatively applied in superstrate Sb2Se3 solar cells, which is further in situ oxidized to wide-bandgap (3.67 eV) tellurium oxide (TeOx). Experimental results indicate that both Te and TeOx layers can enhance the built-in potential and depletion width of devices and reduce nonradiative recombination at back interfaces. Furthermore, the TeOx layer enables better hole transportation due to the favorable band alignment at Sb2Se3/TeOx interfaces. As a congener of Selenium (Se), the Te component of TeOx is found to effectively passivate the selenium vacancy (VSe) defects at the surface of Sb2Se3 absorbers. Consequently, the all-inorganic devices with TeOx show a high voltage of 0.463 V and a champion power conversion efficiency of 9.67%, which is one of the highest efficiencies for the Sb2Se3 solar cells based on vacuum coating technology. This study provides a unique and useful back contact modification strategy for high-performance Sb2Se3 solar cells.