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

Abstract

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 the cold pressing combined with annealing treatment in Ag/Ag₂Se composite films, leading to the reduction of interfaces and the formation of conductive pathways in the films; simultaneously, the crystal 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 a highest power factor of 2139.27 μW m^-1 K^⁻2 was acquired for the films at 360 K. The electrical conductivity of Ag/Ag2Se composite films can maintain 94.2% after bending for 1000 cycles at a radius of 4 mm, revealing 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.