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Flexible thin films of mixed ion−electron conductor Ag 2 Se are an attractive candidate for wearable thermoelectric applications near room temperature. In this work, deposition of Se/Ag 2 Se 1−δ bi-layers by simple thermal evaporation followed by annealing enhances the Se content in the Ag 2 Se 1−δ films. The Se enrichment of the Ag 2 Se 1−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.

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