Advancing Ag2Se thin-film thermoelectrics via selenization-driven anisotropy control
Tianyi Cao1, Xiao-Lei Shi2, Boxuan Hu1
1School of Chemistry and Physics, ARC Research Hub in Zero-emission Power Generation for Carbon Neutrality, and Centre for Materials Science, Queensland University of Technology, Brisbane, QLD, Australia.
Nature Communications
|February 11, 2025
Summary
We developed a wet-chemical method to optimize silver selenide (Ag2Se) thin film orientation for enhanced thermoelectric performance. This technique yields a high power factor and durable, flexible films suitable for practical applications.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Physics
Background:
- The orientation of silver selenide (Ag2Se) thin films significantly impacts their thermoelectric properties, with a common challenge being the detrimental effect of (002) planes on charge carrier mobility.
- Optimizing film orientation is crucial for advancing thermoelectric device efficiency.
Purpose of the Study:
- To develop a novel wet-chemical selenization technique for controlling the in-plane orientation of Ag2Se thin films.
- To enhance the thermoelectric performance of Ag2Se thin films by steering their orientation away from charge carrier mobility-hindering planes.
- To evaluate the durability, flexibility, and device-level performance of the optimized Ag2Se thin films.
Main Methods:
- A wet-chemical selenization process was employed to precisely control the anisotropy and in-plane orientation of Ag2Se thin films.
- The crystallographic orientation was analyzed to confirm the steering away from (002) planes.
- Thermoelectric performance, including power factor, was measured at various temperatures.
- Durability was assessed through prolonged air exposure, and flexibility was tested via bending cycles.
- A slotted thermoelectric device was fabricated and characterized for output power and power density.
Main Results:
- Achieved a high power factor of 30.8 μW cm⁻¹ K⁻² at 343 K.
- The Ag2Se thin films exhibited excellent stability, retaining over 90% of their power factor after six months in air.
- Demonstrated remarkable flexibility, with less than 5% performance variation after 2000 bending cycles (5 mm radius).
- The fabricated thermoelectric device delivered an output power of 0.58 μW and a normalized power density of 1.8 μW cm⁻² K⁻² at a 20 K temperature difference.
Conclusions:
- The developed wet-chemical selenization technique effectively controls Ag2Se thin film orientation, significantly boosting thermoelectric performance.
- The resulting Ag2Se thin films possess exceptional durability and flexibility, making them promising for flexible thermoelectric applications.
- The study provides a viable pathway for designing high-performance, robust, and flexible thermoelectric thin films for practical energy harvesting devices.
