Al-doped Bi₂Se₃ nanoparticulate semiconductors with controlled resonance states for enhanced thermoelectric efficiency

Abstract

The generally lower thermoelectric figure of merit (zT < 0.1) of eco-friendly Bi2Se3 semiconductors constrains the waste energy conversion efficiency in the resulting devices compared to a relatively toxic Bi2Te3. We strategically introduce an aluminium (Al) dopant to create resonance states near the Fermi level and obtain Al–Bi2Se3 nanoparticulate semiconductors with enhanced zT. As an electron feeder, these resonance states significantly improve transport properties within the Al–Bi2Se3 semiconductors. The theoretical calculation shows the creation of the resonance states by hybridizing the dopant's s-orbitals with the host's p-orbitals near the Fermi level. The Al–Bi2Se3 semiconductors effectively moderate electron concentration and the Seebeck-dependent effective mass, resulting in an ultrahigh zT of 0.57 over a broad temperature range of 300–473 K. The nanoparticle size (20 nm) efficiently impedes the propagation of lattice vibration, leading to an ultralow total thermal conductivity of 0.399 Wm−1/K. In contrast to conventional doping approaches, our strategic resonance doping is pivotal to enhancing the thermoelectric performance of the Bi2Se3 semiconductors and providing a pathway for synthesizing other semiconductor materials.