Directed Hot-Electron Transport in Quasi-One-Dimensional Antimony Selenide.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Photovoltaics

Background:

• Extracting hot carriers before thermalization is crucial for exceeding the Shockley-Queisser limit in solar cells and optoelectronics.
• Antimony selenide (Sb₂Se₃) shows potential for hot-carrier applications due to its unique quasi-one-dimensional structure.
• Directly observing ultrafast hot-carrier extraction currents has been a significant challenge.

Purpose of the Study:

• To visualize and characterize the transient hot-electron extraction current at the Sb₂Se₃/SnO₂ interface.
• To identify the energy threshold for hot-electron generation and extraction.
• To establish THz emission spectroscopy as a tool for studying hot-carrier dynamics in Sb₂Se₃.

Main Methods:

• Utilized polarization-phase-resolved THz emission spectroscopy.
• Employed a Fowler-type photoemission model to determine the photon energy threshold.
• Investigated the Sb₂Se₃/SnO₂ heterostructure.

Main Results:

• Successfully visualized directed transient hot-electron extraction currents at the Sb₂Se₃/SnO₂ interface.
• Identified an approximately 1.2 eV pump photon energy threshold, consistent with Sb₂Se₃'s direct band gap.
• Demonstrated the capability of THz emission spectroscopy for noncontact measurement of ultrafast and anisotropic hot-carrier dynamics.

Conclusions:

• THz emission spectroscopy is a powerful technique for mapping ultrafast hot-carrier dynamics.
• The findings provide essential design principles for managing hot carriers in Sb₂Se₃-based energy devices.
• This work advances the understanding of hot-carrier utilization in next-generation photovoltaic and optoelectronic applications.