A Solution Processable High‐Performance Thermoelectric Copper Selenide Thin Film

A solid-state thermoelectric device is attractive for diverse technological areas such as cooling, power generation and waste heat recovery with unique advantages of quiet operation, zero hazardous emissions, and long lifetime. With the rapid growth of flexible electronics and miniature sensors, the low-cost flexible thermoelectric energy harvester is highly desired as a potential power supply. Herein, a flexible thermoelectric copper selenide (Cu2 Se) thin film, consisting of earth-abundant elements, is reported. The thin film is fabricated by a low-cost and scalable spin coating process using ink solution with a truly soluble precursor. The Cu2 Se thin film exhibits a power factor of 0.62 mW/(m K2 ) at 684 K on rigid Al2 O3 substrate and 0.46 mW/(m K2 ) at 664 K on flexible polyimide substrate, which is much higher than the values obtained from other solution processed Cu2 Se thin films (<0.1 mW/(m K2 )) and among the highest values reported in all flexible thermoelectric films to date (≈0.5 mW/(m K2 )). Additionally, the fabricated thin film shows great promise to be integrated with the flexible electronic devices, with negligible performance change after 1000 bending cycles. Together, the study demonstrates a low-cost and scalable pathway to high-performance flexible thin film thermoelectric devices from relatively earth-abundant elements.