In the realm of energy materials research, a team of scientists from the University of Engineering and Technology, Lahore, Pakistan, led by Muhammad Usman Javed, has been exploring innovative ways to enhance the properties of bismuth telluride (Bi2Te3), a material widely used in thermoelectric devices. Their recent study, published in the journal Physical Review Applied, delves into the effects of copper (Cu) doping on the multifunctional properties of Bi2Te3, offering promising avenues for the energy sector.
The researchers employed density functional theory with spin-orbit coupling to investigate the structural, electronic, optical, thermoelectric, and piezoelectric properties of both pristine and Cu-doped Bi2Te3. They found that the substitution of Cu slightly expands the lattice and lowers the total energy minimum, thereby stabilizing the structure. This doping strategy introduces Cu d and Te p hybridization, creating sharp states near the Fermi level. Consequently, the carrier concentration increases, supporting a higher Seebeck coefficient and power factor, which are crucial for efficient thermoelectric energy conversion.
Transport calculations revealed an increase in the Seebeck coefficient from about 180 microvolts per kelvin in pristine Bi2Te3 to about 220 microvolts per kelvin at 300 K, while maintaining nearly unchanged electrical conductivity. This enhancement suggests that Cu doping can improve the thermoelectric performance of Bi2Te3 without compromising its electrical properties. The optical spectra of the doped material showed strong low-energy absorption and very large static dielectric constants (greater than 600), indicating tunable light-matter coupling. This property could be leveraged for applications in infrared detection and optoelectronic devices.
The study also highlighted significant improvements in the piezoelectric properties of Bi2Te3 upon Cu doping. The piezoelectric coefficient e33 increased from 0.19 C/m2 in pristine Bi2Te3 to 0.38 C/m2 at 5 percent Cu and 0.51 C/m2 at 10 percent Cu. This enhancement is attributed to symmetry breaking and strain-driven polarization, making the material more suitable for energy harvesting applications. Charge density difference maps showed anisotropic redistribution, with Cu donating about 0.8 electrons mainly to Te sites. This enhances the p-type behavior and phonon scattering, further contributing to the material’s multifunctional properties.
The researchers concluded that Cu doping reshapes Bi2Te3 into a multifunctional material with coupled thermoelectric, piezoelectric, and optical responses. This makes it suitable for hybrid energy harvesting, infrared detection, and spin-based devices. The findings offer practical applications for the energy sector, particularly in developing more efficient thermoelectric and piezoelectric materials for waste heat recovery and energy conversion systems.
Source: Physical Review Applied
This article is based on research available at arXiv.