KAgX (X = S, Se): High-Performance Layered Thermoelectric Materials for Medium-Temperature Applications

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Monolayer KAgX are novel 2D layered materials with promising optical and electronic properties.
• Potential applications in photovoltaic (PV) and thermoelectric (TE) fields are suggested by their characteristics.

Purpose of the Study:

• Systematically investigate the thermoelectric performance of KAgS and KAgSe monolayers.
• Evaluate their potential for energy conversion applications.

Main Methods:

• Density functional theory (DFT) calculations.
• Semiclassical Boltzmann transport equation (BTE) for transport properties.
• Analysis of thermal conductivity, Seebeck coefficient, and ZT values.

Main Results:

• Ultralow thermal conductivity (0.26 W m^-1 K^-1 for KAgSe, 0.33 W m^-1 K^-1 for KAgS at 300 K) due to hindered heat transport.
• High Seebeck coefficients attributed to electronic band structure features near the Fermi level.
• Achieved ZT values as high as 4.65 (KAgSe) and 4.05 (KAgS) at 500 K for n-type doping.

Conclusions:

• KAgX monolayers demonstrate exceptional thermoelectric performance, particularly at medium temperatures (300-500 K).
• Their ultralow thermal conductivity and excellent electronic transport make them highly promising for thermoelectric devices.
• Results stimulate further experimental synthesis and validation of these 2D materials.