Texture and Se vacancy optimization induces high thermoelectric performance in Bi₂Se₃ flexible thin films

Bi₂Se₃-based flexible thin film with high thermoelectric performance is promising for the waste heat recovery technology. In this work, a novel post-selenization method is employed to prepare n-type Bi₂Se₃ flexible thin films with highly textured structure. The strengthened texture and Se vacancy optimization can be simultaneously achieved by optimizing the selenization temperature. The highly oriented texture leads to the increased carrier mobility and results in a high electric conductivity of ~ 290.47 S·cm⁻¹ at 623 K. Correspondingly, a high Seebeck coefficient (> 110 μW·K⁻¹) is obtained due to the reduced carrier concentration, induced by optimizing vacancy engineering. Consequently, a high power factor of 3.49 μW·cm⁻¹·K⁻² at 623 K has been achieved in as-prepared highly-bendable Bi₂Se₃ flexible thin films selenized at 783 K. This study introduces an effective post-selenization method to tune the texture structure and vacancies of Bi₂Se₃ flexible thin films, and correspondingly achieves high thermoelectric performance.