Flexible oriented α-Cu2Se films and devices with remarkable power factor and output power at near-room temperature

Cu2Se has attracted great attention as a new promising thermoelectric (TE) material because of its high performance, environmentally friendly features and low cost. So far, most studies on Cu2Se focused on the β-phase bulks at medium temperature. However, in terms of commercial applications, α-phase Cu2Se with high TE performance at near-room temperature are highly desired, especially for the flexible thin films which have unique advantages in constructing wearable microelectronic devices. Herein, flexible b-axis oriented α-phase Cu2Se thin films are prepared by pulsed laser deposition (PLD) technology. The in-plane PF of the obtained flexible thin films reaches up to ∼17.6 μW cm−1K−2 at room temperature, which is much higher than that report for Cu2Se random-oriented bulks. In addition, flexible TE thin film devices are developed based on the oriented α-Cu2Se films with ∼3% fluctuation in resistance after bending for 1500 times. The maximum power density of the device is as high as ∼10.2 W m−2 under temperature difference of ∼40 K. Expectedly, the remarkable PF and output power of the thin films and devices as well as the preparation technology with precise controllable proportion will further promote the application of flexible TE materials as self-sufficient energy sources in wearable electronic devices.