High-Performance Printed Ag₂Se/PI Flexible Thermoelectric Film for Powering Wearable Electronics

We report the magnificent thermoelectric properties of the n-type Ag₂Se film printed onto a flexible polyimide (PI) substrate. The orthorhombic β-Ag₂Se phase of the processed Ag₂Se film is confirmed from the X-ray diffractogram. Remarkably, the resulting Ag₂Se/PI film exhibits outstanding thermoelectric properties, boasting maximum power factors of 1.4 and 2.1 mW/mK² at 300 and 405 K, respectively. Furthermore, the flexibility of the Ag₂Se/PI film remains intact even after undergoing 1500 bending cycles with no degradation observed in its thermoelectric performance. To demonstrate the practical application of our findings, a flexible thermoelectric prototype is constructed using the fabricated Ag₂Se/PI films, which can harvest an impressive output voltage of 52 mV across a temperature difference of 53 K. Additionally, the prototype generates a maximum power output of 7.2 μW with a 40 K temperature difference and can produce 13 mV output voltage when subjected to around a 10 K temperature gradient when the cold side temperature is maintained at 308 K. Moreover, leveraging body heat with just a 1 K temperature variance between the body and the surrounding environment, the prototype could yield an impressive voltage output of 1.6 mV, marking the highest reported voltage output from human body heat to date. Our study not only introduces a cost-effective method for producing high-performance flexible thermoelectric films but also highlights their potential applications in wearable and implantable electronics.