Monolayer (ML) transition-metal dichalcogenides are considered as promising channel materials in next-generation transistors. Using ab initio energy band calculations and more reliable ab initio quantum transport simulations, we study the interfacial properties of ML MoSe 2 −metal interfaces (metals = Al, Ag, Pt, Cr, Ni, and Ti). Weak or medium adsorption is found between ML MoSe 2 and the Al, Ag, and Pt surfaces with the band structure of ML MoSe 2 preserved, while strong adsorption is found between ML MoSe 2 and the Ni, Ti, and Cr surfaces with the band structure of ML MoSe 2 destroyed. The two methods give similar polarity and height of Schottky barriers for ML MoSe 2 with Al, Ag, Pt, and Ti electrodes. ML MoSe 2 forms an n-type Schottky contact with Ag, Ti, and Al electrodes with electron Schottky barrier heights (SBH) of 0.25, 0.29, and 0.56 eV, respectively, and a p-type Schottky contact with Pt electrode with hole SBH of 0.78 eV according to ab initio quantum transport simulations. Our study offers a guidance for the choices of suitable metal electrodes in ML MoSe 2 devices.

Cu 9 S 5 (digenite) is a p-type semiconductor with excellent electrical conductivity, high mobility of copper ions, and high work function. When used as the back electrode of CdTe solar cells, a high power conversion efficiency (PCE) is obtained. Density functional theory (DFT) method was used to study the structural and electronic properties of Cu 9 S 5 in this work. From the calculated band structures, we find that the Fermi level of the Cu 9 S 5 slightly crosses the valence band by about 0.08 eV below the valence band maximum (VBM), indicating a high hole concentration and potential high electrical conductivity as a p-type semiconductor. It is also found that the crystal structure of Cu 9 S 5 remained stable with a few Cu atoms diffused away, which introduces a p-type doping effect. Finally, we give a quantitative discussion on why CdTe solar cells with Cu 9 S 5 as the back electrode shows the high PCE.

Specific capacity and cyclic performance are critically important for the electrode materials of rechargeable batteries. Herein, a capacity boost effect of Li- and Na-ion batteries was presented and clarified by nitrogen-doped graphene sheets. The reversible capacities progressively increased from 637.4 to 1050.4 mAh g (164.8% increase) in Li-ion cell tests from 20 to 185 cycles, and from 187.3 to 247.5 mAh g (132.1% increase) in Na-ion cell tests from 50 to 500 cycles. The mechanism of the capacity boost is proposed as an electrochemical induced cascading evolution of graphitic N to pyridinic and/or pyrrolic N, during which only these graphitic N adjacent pyridinic or pyrrolic structures can be taken precedence. The original and new generated pyridinic and pyrrolic N have strengthened binding energies to Li/Na atoms, thus increased the Li/Na coverage and delivered a progressive capacity boost with cycles until the entire favorable graphitic N transform into pyridinic and pyrrolic N.

Systematic study on the doping effects of anatase TiO2 doped with 40 kinds of elements by high-throughput HSE06 calculations.

Li-excess configuration can enhance Li diffusion by introducing two fast channels in spinel lithium manganese oxide.