Layered Germanium-Selenium Compounds as Phonon-Glass Electron-Crystals: A Pathway to Enhance the Thermoelectric...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• The
• phonon-glass electron-crystal
• concept aims to enhance thermoelectric materials by decoupling phonon and electron transport.
• Layered Germanium-Selenium (Ge-Se) crystals exhibit glass-like phonon transport, making them potential candidates for this concept.

Purpose of the Study:

• To theoretically investigate the thermoelectric figure of merit (ZT) in layered Ge-Se crystals.
• To explore the potential of achieving high ZT values by leveraging glass-like phonon transport and carrier doping.

Main Methods:

• Utilized *ab initio* lattice dynamics to model phonon transport.
• Employed the rigid electronic band method to calculate electronic properties.
• Simulated thermoelectric performance under varying electron doping concentrations.

Main Results:

• Predicted an ultrahigh ZT of 4.04 at 1000 K along the *a* axis in the GeSe₂ phase with electron doping of 10²⁰ cm^-3.
• Achieved a high ZT of 2.19 at 600 K along the *a* axis in the Ge₄Se₉ phase with electron doping of 6 × 10¹⁹ cm^-3.
• Observed ultralow lattice thermal conductivity (0.168 W m^-1 K^-1 for GeSe₂ at 1000 K) and high power factors.

Conclusions:

• Layered Ge-Se crystals demonstrate significant potential for high thermoelectric performance.
• Tailoring carrier doping in these materials can effectively maximize the thermoelectric figure of merit (ZT).
• The findings support the viability of the
• phonon-glass electron-crystal
• strategy in layered materials.