Microstructurally Tailored Thin β-Ag₂ Se Films toward Commercial Flexible Thermoelectrics

Aiming to overcome both the structural and commercial limitations of flexible thermoelectric power generators, an efficient room-temperature aqueous selenization reaction that can be completed in air within less than 1 min, to directly fabricate thin β-Ag₂ Se films consisting of perfectly crystalline and large columnar grains with both in-plane randomness and out-of-plane [201] preferred orientation, is designed. A high power factor (PF) of 2590 ± 414 µW m^-1 K^-2 and a figure-of-merit (zT) of 1.2 ± 0.42 are obtained from a sample with a thickness of ≈1 µm. The maximum output power density of the best 4-leg thermoelectric generator sample reach 27.6 ± 1.95 and 124 ± 8.78 W m^-2 at room temperature with 30 and 60 K temperature differences, respectively, which may be useful in future flexible thermoelectric devices.