Hot Carrier and Surface Recombination Dynamics in Layered InSe Crystals

Area of Science:

• Materials Science
• Condensed Matter Physics
• Photovoltaics

Background:

• Layered indium selenide (InSe) is a van der Waals material with potential for high-performance ultrathin solar cells.
• Key optoelectronic parameters like hot carrier lifetime and surface recombination velocity are largely unexplored in InSe.

Purpose of the Study:

• To measure and analyze the photophysical properties of layered InSe relevant to solar cell performance.
• To investigate hot carrier cooling mechanisms and quantify surface recombination velocity and ambipolar diffusion coefficient.

Main Methods:

• Femtosecond transient reflection spectroscopy was employed to study layered InSe.
• A free carrier diffusion model was used to analyze pump energy-dependent transient reflection kinetics.

Main Results:

• Hot carrier cooling in InSe occurs via phonon scattering.
• The surface recombination velocity in InSe is approximately ten times higher than in methylammonium lead-iodide perovskites.
• The ambipolar diffusion coefficient in InSe aligns with previously reported carrier mobility values.

Conclusions:

• Surface recombination is a major contributor to photocarrier loss in InSe solar cells.
• Understanding these photophysical properties is crucial for optimizing InSe-based photovoltaic devices.