Flexible pCu2Se-nAg2Se thermoelectric devices via in situ conversion from printed Cu patterns

Flexible thermoelectric (TE) devices have great potential in wearable electronics, but there is great challenge to realize robust TE device with high performance via feasible integration process. Herein, based on precisely printed copper patterns, a flexible pCu(2)Se-nAg(2)Se TE device is initially realized by in situ ion exchange reaction. The as-prepared Cu2Se and Ag2Se films possess typical hierarchical defects including atomic scale vacancies, the nanosheet fragments and microscale porous structure, which could significantly scatter phonons in wide frequency range. Accordingly, ultra-low thermal conductivity (Cu2Se: 0.13 W m(-1) K-1; Ag2Se: 0.15 W m(-1) K-1) and optimal ZTs (Cu2Se: 0.5; Ag2Se: 0.7) are achieved. Meanwhile, the as-fabricated pCu(2)Se-nAg(2)Se TE device exhibits an excellent power density of 13.4 W m(-2) at a temperature gradient of 40 K, which is among the highest values of printed in-plane film devices. Furthermore, the good adhesion between TE films and porous PI substrate endowed excellent flexibility and stability of pCu(2)Se-nAg(2)Se devices.

Automated summary

Flexible pCu(2)Se-nAg(2)Se thermoelectric devices were successfully realized using precisely printed copper patterns. The Cu2Se and Ag2Se films obtained exhibited hierarchical defects that significantly scattered phonons, resulting in low thermal conductivity and optimal thermoelectric performance. The devices showed excellent power density and flexibility stability.