New frontier in printed thermoelectrics: Formation of β-Ag$_{2}$Se through thermally stimulated dissociative adsorption leads to high ZT

Printed thermoelectrics (TE) could significantly reduce the production cost of energy harvesting devices by large-scale manufacturing. However, developing a high performance printable TE material is a substantial challenge. In this work, a new one-pot synthesis and processing of high performance Ag$_{2}$Se based n-type printed TE materials is reported. Structural analyses reveal that orthorhombic β-Ag$_{2}$Se is the dominant phase in the n-type printed material compounds. For a printed material at room temperature, a breakthrough power-factor of ∼17 μW cm$^{-1}$ K$^{-2}$ with a record high figure-of-merit ZT ∼ 1.03 is achieved. A high average ZT, an important parameter for device applications, of ∼0.85–0.60 has been realized in the temperature range of 300 K to 400 K. Using this material for n-type legs in combination with commercially available PEDOT:PSS for p-type legs, a printed TE generator (print-TEG) of two thermocouples has been fabricated. An output voltage of 17.6 mV and a high maximum power output P$_{max}$ of 0.19 μW are achieved using the print-TEG at ΔT = 75 K.