In situ crystal-amorphous compositing inducing ultrahigh thermoelectric performance of p-type Bi_0.5Sb_1.5Te₃ hybrid thin films

Flexible Bi_0.5Sb_1.5Te₃-based thermoelectric thin films are promising p-type candidates for applications in flexible and wearable electronics. Here, we use thermal evaporation deposition and subsequent post-annealing treatment to prepare Bi_0.5Sb_1.5Te₃ crystal-amorphous hybrid thin films. Tuning the annealing temperature can achieve an optimized hybrid level between amorphous and crystalline Bi_0.5Sb_1.5Te₃, leading to an optimized figure of merit as high as ~1.5 at room temperature, which is an ultrahigh value in the p-type Bi_0.5Sb_1.5Te₃ thin films. Our single parabolic band model and Density-Functional Theory calculation results indicate that such a high value should be attributed to the high effective mass induced by the proper crystal-amorphous hybrid structure. Our study indicates that a crystal-amorphous compositing can be used as a new methodology to achieve ultrahigh performance in thermoelectric materials.