Enhanced performance of n-type Ag2Se thin films via texture engineering
Flexible thermoelectric power generation offers a route to self-powered wearable electronics, but n-type flexible thin films have lagged in performance. This work reports n-type Ag2Se thin films fabricated by thermal evaporation with Se precursor strategies, yielding a (201)-textured orientation. The optimized S-AF films exhibit a dense microstructure with trace nanopores and achieve a power factor of 2.14 mW m−1 K−2 at 300 K, the highest reported for thermally evaporated Ag2Se films. First-principles calculations confirm that the (201) orientation enhances carrier mobility, while Se nano-inclusions and Ag2Se/Se and Ag2Se/Ag heterointerfaces contribute to a high Seebeck coefficient via energy filtering. The inherent low thermal conductivity of Ag2Se is further reduced by nanopores, random in-plane orientation, and heterogeneous interfaces, which scatter phonons across a broad wavelength spectrum. Consequently, an optimal ZT of 0.73 at 363 K is obtained. This study demonstrates that crystallographic texture engineering is a viable strategy to decouple electrical and thermal transport in flexible thermoelectric films, providing a pathway for high-performance wearable energy harvesters.