Bi₂Te₃ single crystals with high room-temperature thermoelectric performance enhanced by manipulating point defects based on first-principles calculation

Abstract

This study prepared Bi2Te3 single crystals and investigated the thermoelectric properties of Bi2Te3 based on the electronic structure and formation energy of point defects which are calculated by density functional theory.

Identifying the Manipulation of Individual Atomic-Scale Defects for Boosting Thermoelectric Performances in Artificially Controlled Bi2Te3 Films

“…In recent years, the Bi 2 Te 3 -based microthermoelectric (TE) devices have found significant and widespread applications in fields, such as precision temperature control of laser diodes, the active cooling of microchips, and the self-powered wearable electronics using human body heat. − It is well-known that the energy conversion efficiency of TE materials depends mainly on the dimensionless thermoelectric figure of merit ZT (defined as ZT = S 2 σ T /κ, where S , σ, κ and T are the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively) . Importantly, the engineering of atomic-scale point defects is among the crucial approaches to optimize the thermoelectric performances of n-Bi 2 Te 3 films, the key component for integrating efficient thin-film TE devices. − …”

“…For decades, nonstoichiometric strategies, ,, Se − or Sb − alloying, as well as doping by foreign elements were primarily approaches for the optimization of the electron density ( n H ) and the power factor ( PF = S 2 σ) of n-Bi 2 Te 3 -based materials. In fact, the TE properties of such heavily extrinsically doped Bi 2 Te 3 were essentially governed by the intrinsic point defects.…”

Improved electrical conductivity and power factor in Sn and Se co-doped melt-grown Bi2Te3 single crystal

“…Usually the single crystal chalchogenides have long-ranged interactions in hexagonal structure. This leads to the strong an-harmonic scattering with different phonon mean-free path results in low value of lattice thermal conductivity [70]. As the anisotropic transport property is exhibited by polycrystalline samples, phonon scattering dominates in the disordered lattice.…”

Quantum Transport and Potential of Topological States for Thermoelectricity in Bi$_2$Te$_3$ Thin Films

“…To maximize the surface diffusion for confining nucleation and growth at the proper atomic sites, the substrate temperature is often tuned to an optimum value. Compared to bulk crystals (typically synthesized at temperatures above 600°C) [36,74], high-quality thin films of Bi 2 Te 3 are grown by MBE at much lower temperatures in the range of 200-350°C [34,35,46,75]. The reduced kinetics at low growth temperatures helps minimize the formation of Te vacancies in MBE-grown thin films.…”

“…By exploiting these properties, Bi 2 Te 3 has been used to fabricate flexible TE devices with a wide range of technological applications, for example in self-powered wearable electronics, electrical power-generation devices and precision temperature control of microchips [26][27][28][29][30][31][32]. Topological surface states and TE properties of Bi 2 Te 3 are intimately related to the position of the Fermi level (E F ) in the electronic band structure [20,[33][34][35] and the concentration of intrinsic defects [36][37][38][39][40][41].…”