High thermoelectric performance via hierarchical compositionally alloyed nanostructures

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Enhancing thermoelectric performance traditionally focused on reducing lattice thermal conductivity via phonon scattering.
• Previous methods often involved broad-spectrum scattering across various length scales.
• Limitations exist in simultaneously optimizing electrical and thermal transport properties.

Purpose of the Study:

• To develop a new design strategy for improving thermoelectric materials.
• To simultaneously enhance both electrical and thermal properties of p-type lead selenide (PbSe).
• To achieve high thermoelectric figure of merit (ZT) in tellurium-free chalcogenides.

Main Methods:

• Employed density functional theory (DFT) to calculate valence band energy levels.
• Investigated nanoscale precipitates of CdS, CdSe, ZnS, and ZnSe for band alignment engineering.
• Engineered electronic structure and band alignment at the nanostructure-matrix interface.
• Alloyed Cadmium (Cd) on the cation sublattice of PbSe.

Main Results:

• Achieved a thermoelectric figure of merit (ZT) of approximately 1.6 at 923 K for p-type PbSe.
• This represents the highest reported ZT for a tellurium-free chalcogenide thermoelectric material.
• Demonstrated favorable valence band alignments between PbSe and alloyed CdSSe/ZnSSe nanostructures.
• Tailored electronic structure by bringing light hole (L) and heavy hole (Σ) valence bands closer in energy.

Conclusions:

• The novel design strategy successfully enhances thermoelectric performance by optimizing both electronic structure and band alignment.
• The achieved ZT value of 1.6 signifies a significant advancement for tellurium-free thermoelectric materials.
• This approach offers a promising pathway for developing high-performance thermoelectric generators.