Fabrication of high-performance flexible Ag/Ag2Se composite films for thermoelectric applications

Abstract

Improving thermoelectric performance of flexible thermoelectric materials is critical for practical implementation of thermoelectric technology in wearable electronic devices and sensors. In this work, Se/Ag₂Se, Ag₂Se, and Ag/Ag₂Se nanoparticles were synthesized via a convenient one-step solution method, and flexible Ag₂Se-based thermoelectric films were fabricated using a vacuum-assisted filtration process. The Ag/Ag₂Se composite nanoparticles were sintered after cold pressing combined with annealing treatment in the Ag/Ag₂Se composite films, leading to the reduction of interfaces and the formation of conductive pathways in the films; simultaneously, the crystallization of Ag and Ag₂Se components was enhanced, and the preferred orientation of Ag₂Se was regulated toward the (013) direction. Consequently, the electrical transport performance of the Ag/Ag₂Se composite films was significantly improved, and the highest power factor of 2139.27 µW m⁻¹ K⁻² was achieved for the films at 360 K. The electrical conductivity of Ag/Ag₂Se composite films remains at 94.2% after bending for 1000 cycles at a radius of 4 mm, revealing the prime flexibility of the sample. A flexible 4-arm thermoelectric generator assembled with Ag/Ag₂Se composite films can generate an open-circuit voltage of 3.99 mV at a temperature difference of ∼11.5 K. Moreover, the Ag/Ag₂Se thermoelectric generator had the ability to respond to external temperature fluctuations, demonstrating its positive temperature sensing capability. This study presents a viable strategy for fabricating flexible high-performance Ag₂Se-based thermoelectric films, and the as-prepared Ag/Ag₂Se composite films show great potential for use in powering wearable electronics and as flexible temperature sensors.