Thermoelectric properties of organic charge transfer salts from first-principle investigations: Role of molecular packing and triiodide anions

The potency of charge transfer (CT) salts in thermoelectric (TE) applications based on (5-CNB-EDT-TTF)4I3 is systematically explored by first-principles calculations combined with Boltzmann transport theory and deformation potential theory, focusing...

Carrier mobility of one-dimensional vanadium selenide (V2Se9) monolayer and nanoribbon systems: DFT study

Vanadium selenide (V2Se9) is a true one-dimensional (1D) crystal composed of atomic nanochains bonded by van der Waals (vdW) interactions. Recent experiments revealed the mechanical exfoliation of newly synthesized V2Se9. In this study, we predicted the electronic and transport properties of V2Se9 through computational analyses. We calculated the intrinsic carrier mobility of V2Se9 monolayers (MLs) and nanoribbons (NRs) using density functional theory and deformation potential theory. We found that the electron mobility of the two-dimensional (2D) (010)-plane ML of V2Se9 is highly anisotropic, reaching μ_(2D,z)^e=1327 cm2 V−1 s−1 across the chain direction. The electron mobility of 1D NR systems in a (010)-plane ML of V2Se9 along the chain direction continuously increased as the thickness increased from 1-chain to 4-chain NR (width below 3 nm). Interestingly, the electron mobility of 1D 4-chain NR along the chain direction (μ_(1D,x)^e=775 cm2 V−1 s−1) was higher than that of a 2D (010)-plane ML (μ_(2D,x)^e=567 cm2 V−1 s−1). These results demonstrate the potential of vdW-1D crystal V2Se9 as a new nanomaterial for ultranarrow (sub-3-nm width) optoelectronic devices with high electron mobility.

High-throughput prediction of the carrier relaxation time via data-driven descriptor

It has been demonstrated that many promising thermoelectric materials, such as tetradymite compounds are also three-dimensional topological insulators. In both cases, a fundamental question is the evaluation of carrier relaxation time, which is usually a rough task due to the complicated scattering mechanisms. Previous works using the simple deformation potential theory or considering complete electron-phonon coupling are, however, restricted to small systems. By adopting a data-driven method named SISSO (Sure Independence Screening and Sparsifying Operator) with the training data obtained via deformation potential theory, we propose an efficient and physically interpretable descriptor to evaluate the relaxation time, using tetradymites as prototypical examples. Without any input from first-principles calculations, the descriptor contains only several elemental properties of the constituent atoms, and could be utilized to quickly and reliably predict the carrier relaxation time of a substantial number of tetradymites with arbitrary stoichiometry.

Oxygen-induced degradation of the electronic properties of thin-layer InSe

The degradation of thin-layer InSe induced by O atoms was quantificationally studied by first-principles calculations and deformation potential theory from the aspects of structural relaxation, band structure, and carrier mobility.

Evaluation of the Key Physical Parameters of Compressive Strained Ge1-x Snx for Optoelectronic Devices

Both strain technology and alloying technology can change the band structures of Germanium semiconductor. This paper focus on evaluation of the key physical parameters, such as energy levels and effective mass, of germanium under strain and alloy conditions, on the basis of deformation potential theory and kp perturbation theory. The results show that: (1), The bandgap transition in Ge1-xSnx alloy cannot occur under strain. So the transformation efficiency of the strained Ge1-xSnx/(001)Ge based devices can not be improved; (2), The various hole effective masses of strained Ge1-xSnx/(001)Ge decrease with the increase of the stress, which benefits to the pMOS performance improvement. Our valid models can provide the valuable references to the design of modified Ge semiconductor and optoelectronic devices.

Electronic property and charge carrier mobility of one-dimensional nanowires consisting of C20 cages

This work presented theoretical studies on the one-dimensional (1D) nanowires constructed from fullerene C20 cages based on first-principle calculations. The relative energies, electronic, charge transport, and mechanical properties of the 1D nanowires were investigated systemically and in detail. It is found that formations of the C20 nanowires built from isolated cages were all energetically favorable. They also exhibit high kinetic stability according to molecular dynamics simulations. Although they were all constructed with C20 cages as building blocks, NW-2–NW-6, and NW-9 are semiconductors, whereas NW-1, NW-7, and NW-8 exhibit metallic property. Thus the metallic/semiconducting properties of the 1D C20 nanowires can be mainly determined by the connecting patterns. High charge mobility was revealed for the 1D C20 nanowires based on the deformation potential theory and effective mass approach. Further understanding of the charge mobility is achieved with the aid of crystal orbital analyses. Moreover, the mechanical property of the 1D C20 nanowires was also studied based on the results of Young’s modulus.

LaPtSb: a half-Heusler compound with high thermoelectric performance

The electronic and transport properties of the half-Heusler compound LaPtSb are investigated by performing first-principles calculations combined with semi-classical Boltzmann theory and deformation potential theory.