Modulation of electronic and optical properties by surface vacancies in low-dimensional β-Ga2O3

2019 ◽  
Vol 21 (27) ◽  
pp. 14745-14752 ◽  
Author(s):  
Yidan Wei ◽  
Chaoming Liu ◽  
Yanqing Zhang ◽  
Chunhua Qi ◽  
Heyi Li ◽  
...  
Keyword(s):  
Optical Properties ◽  
Hybrid Functional ◽  
Electronic And Optical Properties ◽  
Low Dimensional

Calculations using the Heyd–Scuseria–Ernzerhof screened hybrid functional reveal the detailed influence that surface vacancies have on the electronic and optical properties of low-dimensional (LD) β-Ga2O3.

The effect of substitutional doping of Yb2+ on structural, electronic, and optical properties of CsCaX3 (X: Cl, Br, I) phosphors: A first-principles study

2021 ◽  
Author(s):  
Rashid Khan ◽  
Kaleem Ur Rahman ◽  
Qingmin Zhang ◽  
Altaf Ur Rahman ◽  
Sikander Azam ◽  
...  
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Dielectric Susceptibility ◽  
Hybrid Functional ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Electronic And Optical Properties ◽  
Substitutional Doping ◽  
Bandgap Semiconductors ◽  
Magnetic Insulator

Abstract Using first-principles calculations, the effects of Yb$^{2+}$ substitutional doping on structural, electronic, and optical properties of a series of perovskite compounds CsCaX$_3$ (X: Cl, Br, I), have been investigated. We employed generalized gradient approximation (GGA) and HSE hybrid functional to study the electronic and optical properties. A series of pristine CsCaX$_3$(X: Cl, Br, I) is characterized as a non-magnetic insulator with indirect bandgap perovskite materials. These phosphor materials are suitable candidates for doping with lanthanide series elements to tune their electronic bandgaps according to our requirements because of their wide bandgaps. The calculated electronic bandgaps of CsCaX$_3$ (X: Cl, Br, I) are 3.7 eV(GGA) and 4.5 eV (HSE) for CsCaI$_3$, 4.5 eV (GGA) and 5.3 eV (HSE) for CsCaBr$_3$, and 5.4 eV (GGA) and 6.4 eV (HSE) for CsCaCl$_3$. According to formation energies, the Yb$^{2+}$ doped at the Ca-site is thermodynamically more stable as compared to all possible atomic sites. The electronic band structures show that the Yb$^{2+}$ doping induces defective states within the bandgaps of pristine CsCaX$_3$. As a result, the Yb$^{2+}$ doped CsCaX$_3$ (X: Cl, Br, I) become the direct bandgap semiconductors. The defective states above the VBM are produced due to the $f$-orbital of the Yb atom. The impurity states near the CBM are induced due to the major contribution of $d$-orbital of the Yb atom and the minor contribution of $s$-orbital of the Cs atom. The real and imaginary parts of the dielectric function, optical reflectivity, electron energy loss spectrum, extinction coefficient, and refractive index of pristine and Yb$^{2+}$ doped CsCaX$_3$ were studied. The optical dispersion results of dielectric susceptibility closely match their relevant electronic structure and align with previously reported theoretical and experimental data. We conclude that the Yb$^{2+}$ doped CsCaX$_3$ (X: Cl, Br, I) are appealing candidates for optoelectronic devices.

scholarly journals First Principles Study on Electronic and Optical Properties of Quinary Copper-based Sulfides and Selenides Cu2HgGe(S1-xSex)4

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Pham Dinh Khang ◽  
Vo Duy Dat ◽  
Dang Phuc Toan ◽  
Vu Van Tuan
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Density Functional ◽  
Hybrid Functional ◽  
Electron Hole ◽  
Functional Theory ◽  
Electronic And Optical Properties ◽  
Pair Separation ◽  
Electron Hole Pair ◽  
Band Transition

Electronic and optical properties of Cu2HgGe(S1-xSex)4 compounds (x = 0, 0.25, 0.5, 0.75, and 1) were revealed by density functional theory (DFT), in which the Heyd-Scuseria-Ernzerhof hybrid functional was used. Dependence of band gap on the Se constituent in Cu2HgGe(S1-xSex)4 was reported. The substitution of Se element basically cause a slightly lattice expansion and minor change of the band gap. Meanwhile, the overlap of Cu and S/Se states becomes more dense leading to better electron/hole pair separation and inter-band transition of photo-excited electrons. The Cu2HgGe(S0.75Se0.25)4 compound was predicted to be very promising absorber due to the low band gap, high absorption rate, and low reflectivity in the incoming light energy range from 0 eV to 2 eV.    

Electronic and optical properties of CsPb2Br5: A first-principles study

2019 ◽  
Vol 33 (22) ◽  
pp. 1950266 ◽  
Author(s):  
Mingge Jin ◽  
Zhibing Li ◽  
Feng Huang ◽  
Weiliang Wang
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Visible Light ◽  
Band Gap ◽  
First Principles ◽  
First Principles Calculations ◽  
Hybrid Functional ◽  
Electronic And Optical Properties ◽  
Optical Absorbance ◽  
Indirect Band Gap

There are conflicting understandings of the electronic and optical properties of CsPb2Br5. We investigated the electronic and optical properties of CsPb2Br5 with first-principles calculations. It is confirmed that CsPb2Br5 is a semiconductor with an indirect band gap of 3.08 eV at GGA/PBE level and 3.72 eV at the HSE06 hybrid functional level. The PBE results demonstrate that the inclusion of SOC slightly reduces the band gap. We calculate the optical absorbance/emission spectrum of CsPb2Br5. It is found the optical absorption edges locate at 360–380 nm, shorter than the wavelength of visible light. Our results support the experimental results of Li et al. [Chem. Commun. 52 (2016) 11296] and Zhang et al. [J. Mater. Chem. C 6 (2018) 446].

scholarly journals Structural, Electronic, and Optical Properties of p-Type Semiconductors Cu2O and ZnRh2O4: A Self-Consistent Hybrid Functional Investigation

2021 ◽  
Vol 2 (4) ◽  
pp. 504-510
Author(s):  
Daniel Fritsch
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Hybrid Functional ◽  
Electronic And Optical Properties ◽  
Conducting Oxides ◽  
Hartree Fock ◽  
Self Consistent ◽  
Potential Applications ◽  
Functional Investigation ◽  
P Type

The p-type semiconductors Cu2O and ZnRh2O4 have been under investigation for potential applications as transparent conducting oxides. Here, we re-evaluate their structural, electronic, and optical properties by means of first-principles calculations employing density functional theory and a recently introduced self-consistent hybrid functional approach. Therein, the predefined fraction α of Hartree–Fock exact exchange is determined self-consistently via the inverse of the dielectric constant ε∞. The structural, electronic, and optical properties will be discussed alongside experimental results, with a focus on possible technological applications.

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