The room-temperature thermoelectric property of PbTe enhanced by mean-free-path filtering

In order to obtain excellent thermoelectric property of PbTe at room temperature, the most effective approach so far has been reducing the phonon thermal conductivity while maintaining the electronic performance. Based on the first-principles calculation, the scattering mechanisms of electrical transport and thermal transport are clarified. The electrical transport as well as thermal transport of PbTe under various mean free path are studied by taking into account electron/hole mean free path and phonon mean free path. The order of contribution to electrical transport is mean free path scattering>polar optical phonon scattering>acoustic deformation potential scattering>ionized impurity scattering. The Norma process dominates the three-phonon scattering channel, while the Umklapp process controls the four-phonon scattering channel. The 80% contribution of lattice thermal conductivity origins from acoustic branch, and the rest is from optical branch. When the hole/phonon mean free path is 10 nm, the ZT of p type is about 0.58, which is nearly four times larger than that of bulk ZT (0.15), implying the mean-free-path filtering is an effective method to enhance the value of ZT.