Ultrafast carrier kinetics at surface and interface of Sb₂Se₃ film by transient reflectance

Abstract

Antimony selenide (Sb₂Se₃) is a promising low-cost and environmentally-friendly semiconductor photovoltaic material. The power conversion efficiency of Sb₂Se₃ solar cells has been improved to <inline-formula><tex-math id="Z-20220322113243-1">\begin{document}$ \sim $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211714_Z-20220322113243-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211714_Z-20220322113243-1.png"/></alternatives></inline-formula>10% in the past few years. The carrier recombination transfer dynamics is significant factor that affects the efficiency of Sb₂Se₃ solar cells. In this work, carrier recombination on the Sb₂Se₃ surface and carrier transfer dynamics at the CdS/Sb₂Se₃ heterojunction interface are systematically investigated by surface transient reflectance. According to the evolution of relative reflectance change <inline-formula><tex-math id="M2">\begin{document}${{\Delta }{R}}/{{R}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211714_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211714_M2.png"/></alternatives></inline-formula>, the carrier thermalization and band gap renormalization time of Sb₂Se₃ are determined to be in a range from 0.2 to 0.5 ps, and carrier cooling time is estimated to be about 3－4 ps. Our results also demonstrate that both free electron and shallow-trapped electron transfer occur at the Sb₂Se₃/CdS interface after photo excitation. Our results present a method of explaining the transient reflectance of Sb₂Se₃ and enhancing the understanding of carrier kinetics at Sb₂Se₃ surface and Sb₂Se₃/CdS interface.