The Effect Of Doping On Electronic And Optical Properties Of LaOF: A First-principles Calculations

In the21st century, the energy crisis and environmental problems have hamperedthe sustainable development, economic development and how to ease thecontradiction between energy and the environment in front of us becoming a seriousproblem. The current common energy are coal, oil, natural gas and othernon-renewable energy sources, the release of toxic combustion gases such as carbonmonoxide, sulfur dioxide and nitrogen oxides, caused the environment and humanhealth great harm, the use of hydrogen can avoid the above problems, and usingsemiconductor photocatalyst to produce hydrogen under the sunshine is an affordableway. LaOF compatibility with good structure, good physical and chemical stability,low phonon energy etc. is a potentially efficient photocatalyst. Photocatalyticproperties of semiconductors depends on the ability of absorb optical and theappropriate redox potential, and the ability to resist the photo-generated electrons andholes fast composite boycott, and these factors with the band gap of a greatrelationship. Research shows that dopant is an effective means to reduce the band gap,and thus extends the edge of the absorption band to the visible region. In this paper,we used first-principles study LaOF doped rare earth elements, halogen elements andoxygen elements, Analysis the affect of the electronic structure and optical properties.Have made the following findings:(1) Investigate the effect of Ce, Pr, Nd and Pm doping on electronic and opticalproperties of LaOF. Found that the bandgap reduced after doped, gradually decreasingwith the order from Ce to Pm doping, while the4f impurity level appears in the bandgap; in the photocatalytic process, electron transitions from the valence band to the4flevel, then transitions from4f level to the conduction band, reducing the energyrequired of electrons transition from the valence band to the conduction band, as aresult the optical properties of the material had a great influence, Nd doped producedtwo4f impurity level, although the band gap is large than the Pm, but its lightabsorption ability is better than Pm doping a little.(2) Investigate the effect of CI, Br and I doping on electronic and opticalproperties of LaOF. Found that the crystal structure distortion after doped, I doping ismost significant, because I element is largest in radius in the halogen element whichwe selected; the bandgap of LaOF reduced after doped, but the three-doped hybrid system is not great difference; from the curve of light absorption we can find that theoptical properties of the doped LaOF is improved, but three doping system is not greatdifference.(3) Investigate the effect of S, Se and Te doping on electronic and opticalproperties of LaOF. Found that the band gap decreases after doping, and decreased inthe order of S to Te; from conduction band of LaOF split up La5d orbit, forming anintermediate level, the energy level can let the electron transition from the valenceband to the conduction band with two steps, and therefore a great influence on theoptical properties of the material; the intermediate level of Te doping movesignificantly, and therefore it’s light absorbing ability is far stronger than the othertwo doping system.