Largely Enhanced Thermoelectric Power Factor of Flexible Cu(2−x)S Film by Doping Mn

Copper-sulfide-based materials have attracted noteworthy attention as thermoelectric materials due to rich elemental reserves, non-toxicity, low thermal conductivity, and adjustable electrical properties. However, research on the flexible thermoelectrics of copper sulfide has not yet been reported. In this work, we developed a facile method to prepare flexible Mn-doped Cu(2−x)S films on nylon membranes. First, nano to submicron powders with nominal compositions of Cu(2−x)Mn(y)S (y = 0, 0.01, 0.03, 0.05, 0.07) were synthesized by a hydrothermal method. Then, the powders were vacuum-filtrated on nylon membranes and finally hot-pressed. Phase composition and microstructure analysis revealed that the films contained both Cu(2)S and Cu(1.96)S, and the size of the grains was ~20–300 nm. By Mn doping, there was an increase in carrier concentration and mobility, and ultimately, the electrical properties of Cu(2−x)S were improved. Eventually, the Cu(2−x)Mn(0.05)S film showed a maximum power factor of 113.3 μW m(−1) K(−2) and good flexibility at room temperature. Moreover, an assembled four-leg flexible thermoelectric generator produced a maximum power of 249.48 nW (corresponding power density ~1.23 W m(−2)) at a temperature difference of 30.1 K, and had good potential for powering low-power-consumption wearable electronics.