研究目的
To measure the hot carrier lifetime and surface recombination velocity in layered InSe crystals, which are critical for photoconversion efficiencies in solar cells.
研究成果
The hot carrier lifetime in InSe is dependent on carrier density and mediated by phonon scattering, with cooling times of 0.61–3.5 ps. The ambipolar diffusion coefficient is 15.1 cm2s?1, consistent with high carrier mobility, and the surface recombination velocity is 4.1×10? cm s?1, indicating intermediate levels of surface recombination. Surface passivation could improve solar cell efficiencies. Future work should optimize measurements for thinner samples and decouple additional electronic transitions.
研究不足
The TR measurement is performed at an oblique reflection angle, which may affect mobility estimates. The study is limited to bulk layered InSe; extension to ultrathin flakes requires further optimization, such as with transient absorption microscopy. Signal-to-noise issues in near-infrared data prevent decoupling of certain transitions.
1：Experimental Design and Method Selection:
Femtosecond transient reflection (TR) spectroscopy was used to study hot carrier and surface recombination dynamics. A free carrier diffusion model (Yang model) was employed to extract parameters like surface recombination velocity and ambipolar diffusion coefficient.
2：Sample Selection and Data Sources:
Layered InSe crystals were grown by the Bridgman method and characterized. Samples were cleaved and prepared in a nitrogen glovebox to avoid degradation.
3：List of Experimental Equipment and Materials:
InSe single crystals, quartz cuvettes, nitrogen glovebox, femtosecond laser system for TR spectroscopy, OriginPro
4：6 software for data analysis. Experimental Procedures and Operational Workflow:
TR spectroscopy was performed on InSe crystals held in N2-filled quartz cuvettes. Measurements were conducted at various pump energies and carrier densities. Data were analyzed using inverse Hilbert transformation and global fitting routines.
5：Data Analysis Methods:
Nonlinear least-squares global fitting was used with the Yang model equation to extract SRV and D values. Hot carrier cooling times were determined from exponential fits of kinetic traces.
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