Electrochemical Synthesis of Polypyrrole/Cu_2-xSe Composites for Enhanced Thermoelectric Performance

Copper selenide compounds, owing to their excellent electrical transport properties and low thermal conductivity, are promising thermoelectric materials, but their poor mechanical flexibility limits practical applications in flexible devices. Herein, a simple all-electrochemical strategy was developed to fabricate polypyrrole (PPy)/Cu_2-xSe composite thermoelectric films through sequential electropolymerization of pyrrole and electrodeposition of Cu_2-xSe. By optimizing the deposition potential of Cu_2-xSe and pyrrole polymerization time, the thermoelectric performance of the composite films was significantly enhanced. The optimized PPy/Cu_2-xSe composite film achieved a maximum power factor of 174.05 ± 9.87 μW m^-1 K^-2, nearly 300 times higher than that of pristine PPy, while maintaining a low thermal conductivity of 0.30 W m^-1 K^-1. The composite film also exhibited excellent flexibility, retaining 94.77% of its initial power factor after 1000 bending cycles. A flexible thermoelectric device assembled from the composite films delivered a maximum output power of 240.5 nW at ΔT = 50 K. This work provides an effective strategy for developing Cu_2-xSe-based flexible thermoelectric composites.