LAUSR

Flexible thermoelectrics provide a different solution for developing portable and sustainable flexible power supplies. The discovery of silver sulfide–based ductile semiconductors has driven a shift in the potential for flexible thermoelectrics, but the lack of good p-type ductile thermoelectric materials has restricted the reality of fabricating conventional cross-plane π-shaped flexible devices. We report a series of high-performance p-type ductile thermoelectric materials based on the composition-performance phase diagram in AgCu(Se,S,Te) pseudoternary solid solutions, with high figure-of-merit values (0.45 at 300 kelvin and 0.68 at 340 kelvin) compared with other flexible thermoelectric materials. We further demonstrate thin and flexible π-shaped devices with a maximum normalized power density that reaches 30 μW cm−2 K−2. This output is promising for the use of flexible thermoelectrics in wearable electronics. Description A flexible power source Thermoelectric materials can harvest heat and turn it into power. Heat sources potentially include the heat generated by humans through wearable devices and might enable self-powering systems, but the lack of ductility for most thermoelectrics poses a major problem. Yang et al. found a thermoelectric silver/copper–based semiconductor that also is ductile (see the Perspective by Hou and Zhu). This material allows for a thin, flexible device capable of producing power, even when adhered to a wrist. —BG A flexible thermoelectric was developed from a silver/copper–based semiconductor that can be fashioned into a thin device.