Effect of post-annealing treatment on the thermoelectric properties of Ag2Se flexible thin film prepared by magnetron sputtering method

Flexible thermoelectric power generation devices can help solve the power supply problem of wearable electronic devices. Herein, single-phase Ag2Se films with a thickness of less than 500 nm were deposited on flexible polyimide substrates via magnetron sputtering. The microstructure, chemical composition, and thermoelectric properties of the films were investigated at different annealing temperatures (523 K–673 K). After annealing, the X-ray diffraction (XRD) test showed that the film had obvious preferential growth in the (0 0 2) and (0 0 4) crystallographic directions. Scanning electron microscopy (SEM) showed that with increasing annealing temperature, the size of the grains initially increased and subsequently decreased. Finally, after annealing at 623 K for 20 min, the film obtained a peak power factor of 526.86 μW∙m−1∙K−2. A six-leg flexible generator comprising Ag2Se films has a maximum power density of 7.52 W∙m−2 (50 K temperature difference). After 1000 bending times, the resistivity of the device changed by only 14.11 %, and the actual application test revealed an output voltage of 12.3 mV and a power of 23.49 nW under a temperature difference of 22.2 K. This work demonstrates that thermal treatment of thin films prepared by magnetron sputtering is a remarkable approach to increase thermoelectric performance, providing an efficient fabrication scheme for the development of environmentally friendly and wearable flexible thermoelectric devices.