High thermoelectric performance at room temperature in electrodeposited Ag2Se and Cu2Se films via microstructural control

Electrodeposited silver selenide (Ag 2 Se) and copper selenide (Cu 2 Se) films are explored as scalable thermoelectric materials at room temperature ( RT ), focusing on the relationship between growth conditions, microstructure, and transport properties. For Ag 2 Se, a maximum in-plane power factor ( PF ) of 7655 ± 1578 μW·m -1 ·K -2 is achieved, placing this material among the highest-performing n- type thermoelectrics in terms of PF at RT . The optimized films (Ag 1.92 Se) exhibit a dense granular morphology, strong (200) orthorhombic orientation, and minimal secondary phases; with an out-of-plane thermal conductivity ( k ) of 0.79 ± 0.16 W·m -1 ·K -1 . For Cu 2 Se, a maximum in-plane PF of 1130 ± 233 μW·m -1 ·K -2 is obtained at RT , representing a five-fold improvement over previous electrodeposited Cu 2 Se films and approaching the highest values reported via vacuum-based methods. The optimized composition (Cu 1.88 Se) shows compact elongated grains and a predominantly cubic structure with (111) orientation; with an out-of-plane k of 0.89 ± 0.18 W·m -1 ·K -1 at RT . The optimized materials were further integrated into a prototype π -type thermoelectric generator, delivering a maximum power density of 8.5 W·m -2 under a temperature gradient of 12 K. These results establish electrodeposition as a simple and scalable platform for tuning microstructure and transport properties in chalcogenide films, yielding competitive thermoelectric performance at RT .