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.