Flexible Te/PEDOT:PSS thin films with high thermoelectric power factor and their application as flexible temperature sensors

Flexible, lightweight, and low-cost thermoelectric thin films are promising for self-powered wearable electronics and sensors. In this work, we report on flexible Te nanostructures/PEDOT:PSS composite thin films with high power factor and their application as flexible temperature sensors. Te nanostructures with high crystallinity and high aspect ratios were synthesized through an environmentally friendly method without using highly toxic chemicals. Individual Te nanostructures achieve a thermoelectric figure of merit (ZT) of 0.13 at 300 K, indicating good potential as inorganic fillers for nanostructures/polymer hybrid materials. Based on the synthesized Te nanostructures, flexible p-type Te/PEDOT:PSS thin films were fabricated through a simple dilution and vacuum filtration method. The power factor of the as-prepared composite thin film outperforms that of either a Te or DMSO-treated PEDOT:PSS thin film, and importantly, it can be further enhanced to 149 μW m^-1 K^-2 by hot pressing, which is nearly threefold enhancement compared to the values reported for the vacuum-filtered flexible Te/PEDOT:PSS thin films in the literature. The hot-pressed composite thin film shows high flexibility with the electrical conductivity remaining almost unchanged after 1000 bending cycles under a bending radius of 5 mm. Flexible temperature sensors were fabricated based on the hot-pressed Te/PEDOT:PSS thin film, which exhibited high sensitivity in detecting temperature stimuli. The developed temperature sensors were applied onto a two-finger flexible mechanical claw for identifying hot/cold objects in robotic grasping. This work demonstrates an effective approach to enhance the thermoelectric power factor of flexible Te nanostructures/polymer composites and their promising application in flexible thermal sensing.