Prefer‐Oriented Ag2Se Crystal for High‐Performance Thermoelectric Cooling

Abstract Ag 2 Se‐based materials with promising room‐temperature thermoelectric performance have been known for decades. However, thermoelectric cooling devices based on bulk Ag 2 Se have seldom been reported, mainly due to the phase transition ≈400 K poses a grand challenge for leg design and module integration. Herein, Ag 2 Se crystals with the preferred orientation have been prepared. A high carrier mobility of ≈1846 cm 2 V −1 s −1 and a power factor of ≈31.2 µW cm −1 K −2 at room temperature has been realized, and results in a zT of ≈0.95 at 300 K. Importantly, by applying Ag as the contact layer, the Ag/Ag 2 Se/Ag joint has been prepared by one‐step sintering. By maintaining the pressure of ≈10 MPa after sintering and during the reflow soldering, the deleterious effect of the large thermal expansion can be alleviated. The contact resistance of the Ag/Ag 2 Se interface is as low as ≈2.9 µΩ cm 2 , indicating negligible electrical parasitic loss. The thermoelectric device with 7 pairs of Ag 2 Se and (Bi, Sb) 2 Te 3 has been fabricated and it can achieve a maximum cooling power of ≈2.90 W and a cooling temperature difference of ≈70.4 K at the hot‐side temperature of 350 K, demonstrating the great potential of Ag 2 Se for cooling applications.