Flexible Thermoelectric Generator Based on Polycrystalline SiGe Thin Films

Area of Science:

• Materials Science
• Energy Harvesting
• Thermoelectrics

Background:

• Flexible thermoelectric generators (TEGs) are crucial for powering future energy harvesting sensors.
• Existing TEG technologies often require high processing temperatures, limiting substrate compatibility and flexibility.

Purpose of the Study:

• To synthesize flexible p- and n-type silicon-germanium (SiGe) layers on polyimide films.
• To demonstrate thermoelectric generator (TEG) operation using these synthesized layers.
• To evaluate the thermoelectric properties and output power of the flexible TEGs.

Main Methods:

• Synthesis of p- and n-type SiGe layers on a polyimide film using metal-induced layer exchange (LE) at temperatures below 500 °C.
• Characterization of the thermoelectric properties, including power factors, of the synthesized SiGe layers.
• Fabrication and testing of an in-plane π-type TEG device.

Main Results:

• Achieved high power factors for polycrystalline SiGe layers: 560 µW m^-1 K^-2 for p-type Si_0.4Ge_0.6 and 390 µW m^-1 K^-2 for n-type Si_0.85Ge_0.15, attributed to self-organized doping during LE.
• Demonstrated stable power factor behavior across varying measurement temperatures, highlighting SiGe's advantage as an inorganic material.
• An in-plane π-type TEG exhibited an output power of 0.45 µW cm^-2 under a 30 K temperature gradient near room temperature.

Conclusions:

• Low-temperature synthesis of flexible SiGe layers via LE enables high-performance thermoelectric energy harvesting.
• The developed flexible TEGs are reliable and suitable for powering micro-energy devices.
• This work paves the way for environmentally friendly and highly reliable flexible TEGs for the Internet of Things.