Enhanced near‐room‐temperature thermoelectric performance in GeTe

Abstract GeTe is an excellent mid‐temperature thermoelectric material with high dimensionless figure of merit ( ZT ) values at temperatures over 600 K. Its near‐room‐temperature performance is less studied due to the intrinsic high carrier concentration. Here, we successfully enhance the Seebeck coefficient of GeTe from ~ 30 to 220 μV·K −1 at 300 K, which is achieved by AgInSe 2 alloying and Bi doping. It is demonstrated that Bi doping helps to optimize the Seebeck coefficient without deteriorating the intrinsic electrical transport properties of the matrix. A high room‐temperature power factor (PF) of ~ 11 μW·cm −1 ·K −2 is achieved for a wide range of Bi‐doped samples. The simultaneously introduced abundant point defects cause mass and strain fluctuations, which decrease the lattice thermal conductivity ( κ L ) to a low value of 0.6 W·m −1 ·K −1 at 300 K. Due to the synergetic effects of Bi doping in AgInSe 2 ‐alloyed GeTe, a high room‐temperature ZT value of 0.46 is obtained together with a high ZT value of 1.1 at 523 K.