Geometric Symmetry Breaking and Nonlinearity Can Increase Thermoelectric Power

Area of Science:

• Solid State Physics
• Materials Science
• Energy Conversion

Background:

• Direct thermal-to-electric energy converters often operate linearly, limiting their efficiency.
• The fill factor (FF), a measure of power conversion efficiency, typically remains low (0.25) in linear devices.

Purpose of the Study:

• To investigate nonlinear effects for enhancing the performance of thermal-to-electric energy converters.
• To explore the role of spatial symmetry in improving the fill factor and maximum power output.

Main Methods:

• Theoretical analysis based on fundamental symmetry considerations.
• Experimental study of nonlinear thermoelectric transport across an asymmetric energy barrier in a semiconductor nanowire.

Main Results:

• Identified that nonlinear terms increasing the FF require broken spatial symmetry.
• Demonstrated experimentally and theoretically that asymmetric energy barriers enhance FF and maximum power.
• Achieved higher performance through geometric symmetry breaking and nonlinear design.

Conclusions:

• Breaking spatial symmetry is a key strategy for improving thermoelectric device performance.
• Nonlinear thermoelectric transport in asymmetric structures offers a pathway to overcome limitations of linear devices.
• This approach is applicable to enhancing both thermoelectric and hot-carrier devices.