Ultrafast carrier kinetics at surface and interface of Sb<sub>2</sub>Se<sub>3</sub> film by transient reflectance

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 \begin{document}$ \sim $\end{document}10% in the past few years. The carrier recombination transfer dynamics is significant factor that affects the efficiency of Sb₂Se₃ solar cells. In this work, carrier recombination on the Sb₂Se₃ surface and carrier transfer dynamics at the CdS/Sb₂Se₃ heterojunction interface are systematically investigated by surface transient reflectance. According to the evolution of relative reflectance change \begin{document}${{\Delta }{R}}/{{R}}$\end{document}, 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.