Improved Power Factor in Highly Textured n-Type Ag₂Se Flexible Films

Flexible thin films of mixed ion–electron conductor Ag2Se are an attractive candidate for wearable thermoelectric applications near room temperature. In this work, deposition of Se/Ag2Se1−δ bi-layers by simple thermal evaporation followed by annealing enhances the Se content in the Ag2Se1−δ films. The Se enrichment of the Ag2Se1−δ films resulted in the improvement of the power factor through improved texturing and an enhanced Seebeck coefficient due to reduced carrier concentration. Films with Se/Ag ratio of ∼0.5 showed the highest power factor of ∼22 μW cm–1 K–2 at 320 K, i.e., 85% higher than that of films with Se/Ag ratio of 0.33. These high-performance films exhibited a very mild reversible change in the Seebeck coefficient and resistance on convex bending. A thermoelectric generator with 10 uni-legs of optimized films showed an outstanding power density of 2.6 W m–2 at a temperature difference of 10 K.