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 (TeO_<i>x</i>). Experimental results indicate that both Te and TeO_<i>x</i> layers can enhance the built-in potential and depletion width of devices and reduce nonradiative recombination at back interfaces. Furthermore, the TeO_<i>x</i> layer enables better hole transportation due to the favorable band alignment at Sb₂Se₃/TeO_<i>x</i> interfaces. As a congener of Selenium (Se), the Te component of TeO_<i>x</i> is found to effectively passivate the selenium vacancy (<i>V</i>_Se) defects at the surface of Sb₂Se₃ absorbers. Consequently, the all-inorganic devices with TeO_<i>x</i> 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.