Advancing thermoelectric and sensing performance in constrained GeTe thin films

Thermoelectric thin films hold significant potential for self-powered microelectronic and advanced sensing devices. However, they normally demonstrate inferior electrical transport performance compared to their bulk counterparts. Herein, we deposited growth-restricted GeTe thin films to improve their electrical transport performance and further employed optical thin films, serving as spectrally selective absorbers and radiative cooling coatings, to enlarge the temperature difference across the thermoelectric legs. Growth-restricted GeTe thin films with high crystallinity were achieved under the confinement effect of the top SiO₂ layer. Due to the increase in carrier mobility, the room-temperature power factor of the GeTe film is significantly improved to 26.1 μW cm^-1 K^-2. In combination with a W-SiO₂-based spectrally selective absorber and PDMS/Ag radiative coating, a thin-film thermoelectric device assembled using the optimized GeTe and Ag₂Se thin films can achieve a temperature difference of 22 K under the AM1.5 spectrum and produce a maximum output power of 0.57 μW. Furthermore, it can sense outdoor weather conditions through the detection of light intensity. These findings demonstrate the potential of the GeTe thin film in both power generation and sensing.