Enhanced thermoelectric performance in the Rashba semiconductor BiTeI through band gap engineering

Area of Science:

• Materials Science
• Condensed Matter Physics

Background:

• Rashba semiconductors are crucial for spintronics, superconducting electronics, and thermoelectrics.
• Bismuth telluride iodide (BiTeI) exhibits a giant spin-split band structure and 2D-like thermoelectric response.
• Optimizing carrier concentration in BiTeI leads to a detrimental bipolar effect at higher temperatures.

Purpose of the Study:

• To engineer the band gap of BiTeI through bromine substitution.
• To mitigate the bipolar effect and enhance thermoelectric performance.
• To investigate the impact of Br-substitution on the electronic band structure and transport properties.

Main Methods:

• Band gap engineering via bromine (Br) substitution in BiTeI.
• Optical absorption spectroscopy.
• Burstein-Moss effect analysis.
• Thermoelectric property measurements.

Main Results:

• Bromine substitution increased the band gap of BiTeI, consistent with theoretical predictions.
• The larger band gap effectively reduced bipolar transport by diminishing thermally-activated minority carriers.
• The Seebeck coefficient increased with temperature, and thermoelectric performance was enhanced.

Conclusions:

• Band gap engineering in BiTeI using Br-substitution is a viable strategy to suppress the bipolar effect.
• Enhanced thermoelectric properties were achieved, reaching a figure of merit (ZT) of 0.5 at 570 K for BiTeI0.88Br0.12.
• This approach offers a pathway for developing improved thermoelectric materials based on Rashba semiconductors.