Prefer‐Oriented Ag₂Se Crystal for High‐Performance Thermoelectric Cooling

Abstract

Ag2Se‐based materials with promising room‐temperature thermoelectric performance have been known for decades. However, thermoelectric cooling devices based on bulk Ag2Se have seldom been reported, mainly due to the phase transition ≈400 K poses a grand challenge for leg design and module integration. Herein, Ag2Se crystals with the preferred orientation have been prepared. A high carrier mobility of ≈1846 cm2 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/Ag2Se/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/Ag2Se interface is as low as ≈2.9 µΩ cm2, indicating negligible electrical parasitic loss. The thermoelectric device with 7 pairs of Ag2Se and (Bi, Sb)2Te3 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 Ag2Se for cooling applications.