Enhanced photocatalytic activities of Bi2WO6 by introducing Zn to replace Bi lattice sites: a first-principles study

RSC Advances ◽  
2015 ◽  
Vol 5 (37) ◽  
pp. 29058-29065 ◽  
Author(s):  
Fengzhu Ren ◽  
Jihua Zhang ◽  
Yuanxu Wang
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
First Principles ◽  
Lone Pair ◽  
Valence Band Maximum ◽  
Zn Doping ◽  
Band Maximum ◽  
Photocatalytic Activities ◽  
Valence Bands ◽  
Density Of Electrons

Zn doping can enhance the stereochemically active Bi lone pair effect at the top of the valence bands of Bi2WO6, which will lead to the decreasing of its band gap and the increasing of the density of electrons in its valence band maximum.

First-Principles Calculations on the Electronic Structure of ZnO Nanowires

2012 ◽  
Vol 198-199 ◽  
pp. 23-27
Author(s):  
Nan Zhang ◽  
Hong Sheng Zhao ◽  
Dong Yang ◽  
Wen Jie Yan
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Density Functional ◽  
Valence Band Maximum ◽  
Zno Nanowires ◽  
Cross Sectional ◽  
Quantum Size

Based upon the density functional theory (DFT) in this paper, the first-principles approach is used to study the electronic structure of different cross-sectional diameters of ZnO [0001] nanowires of wurtzite structure. The results show that ZnO [0001] nanowires have a wide direct band gap. Located in the G-point of the Brillouin zone the conduction band minimum and valence band maximum are relatively smooth. The conduction band is mainly composed of Zn 4s and Zn 4p states, and the valence band is composed of Zn 3d and O 2p states. The effective mass of conduction band electrons and valence band holes are large while their mobility is very low which show that conductive ability of pure defect-free [0001] ZnO nanowires is weak. Along with the increase of the cross-sectional diameters, the band gap gradually decreases that indicates quantum size effects are obvious in the nano size range.

scholarly journals Machine Learning Chemical Guidelines for Engineering Electronic Structures in Half-Heusler Thermoelectric Materials

Research ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Maxwell T. Dylla ◽  
Alexander Dunn ◽  
Shashwat Anand ◽  
Anubhav Jain ◽  
G. Jeffrey Snyder
Keyword(s):  
Machine Learning ◽  
Valence Band ◽  
Electronic Structures ◽  
Electronic Band Structure ◽  
Valence Band Maximum ◽  
Electronic Band ◽  
Band Maximum ◽  
Orbital Phase ◽  
Valence Bands ◽  
P Type

Half-Heusler materials are strong candidates for thermoelectric applications due to their high weighted mobilities and power factors, which is known to be correlated to valley degeneracy in the electronic band structure. However, there are over 50 known semiconducting half-Heusler phases, and it is not clear how the chemical composition affects the electronic structure. While all the n-type electronic structures have their conduction band minimum at either the Γ- or X-point, there is more diversity in the p-type electronic structures, and the valence band maximum can be at either the Γ-, L-, or W-point. Here, we use high throughput computation and machine learning to compare the valence bands of known half-Heusler compounds and discover new chemical guidelines for promoting the highly degenerate W-point to the valence band maximum. We do this by constructing an “orbital phase diagram” to cluster the variety of electronic structures expressed by these phases into groups, based on the atomic orbitals that contribute most to their valence bands. Then, with the aid of machine learning, we develop new chemical rules that predict the location of the valence band maximum in each of the phases. These rules can be used to engineer band structures with band convergence and high valley degeneracy.

STRAIN-TUNABLE BAND GAP OF BC3 SHEET: A FIRST-PRINCIPLES INVESTIGATION

2013 ◽  
Vol 27 (15) ◽  
pp. 1350110 ◽  
Author(s):  
GANG LIU ◽  
MU SHENG WU ◽  
CHU YING OUYANG ◽  
BO XU
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Tensile Strain ◽  
Compressive Strain ◽  
Valence Band Maximum ◽  
Functional Theory ◽  
Band Maximum ◽  
Tunable Band Gap

The effect of strain on the electronic properties of BC 3 sheet was studied by using first-principles density functional theory. It is found that the band gap of BC 3 sheet increases gradually when the applied tensile strain ranges from 0% to 12.5%. While the band gap decreases as the compressive strain is applied, especially resulting in the semiconductor-metal transition at some strain. Further analysis shows that the change of band gap mainly results from the variation of the energy of valence band maximum (VBM), which is related to the strength of the bonding state. The proposed mechanical control of the electronic properties will widen the application of BC 3 sheet in future nanotechnology.

scholarly journals A first-principles study of anionic (S) and cationic (V/Nb) doped Sr2Ta2O7 for visible light photocatalysis

RSC Advances ◽  
2017 ◽  
Vol 7 (65) ◽  
pp. 40922-40928 ◽  
Author(s):  
Yuman Peng ◽  
Zuju Ma ◽  
Junjie Hu ◽  
Kechen Wu
Keyword(s):  
Visible Light ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Valence Band Maximum ◽  
Conduction Band Minimum ◽  
Visible Light Photocatalysis ◽  
Band Maximum ◽  
Co Doping ◽  
First Principles Study

In order to utilize the visible light to catalyze water, UV-active Sr2Ta2O7 is engineered via co-doping of S and V/Nb to shift the valence band maximum upward and conduction band minimum downward by approximately 1 eV, respectively.

scholarly journals An antibonding valence band maximum enables defect-tolerant and stable GeSe photovoltaics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shun-Chang Liu ◽  
Chen-Min Dai ◽  
Yimeng Min ◽  
Yi Hou ◽  
Andrew H. Proppe ◽  
...  
Keyword(s):  
Solar Cells ◽  
Valence Band ◽  
Surface Passivation ◽  
Defect Density ◽  
Perovskite Solar Cells ◽  
Valence Band Maximum ◽  
Ambient Conditions ◽  
Band Maximum ◽  
Point Tracking ◽  
Power Point

AbstractIn lead–halide perovskites, antibonding states at the valence band maximum (VBM)—the result of Pb 6s-I 5p coupling—enable defect-tolerant properties; however, questions surrounding stability, and a reliance on lead, remain challenges for perovskite solar cells. Here, we report that binary GeSe has a perovskite-like antibonding VBM arising from Ge 4s-Se 4p coupling; and that it exhibits similarly shallow bulk defects combined with high stability. We find that the deep defect density in bulk GeSe is ~1012 cm−3. We devise therefore a surface passivation strategy, and find that the resulting GeSe solar cells achieve a certified power conversion efficiency of 5.2%, 3.7 times higher than the best previously-reported GeSe photovoltaics. Unencapsulated devices show no efficiency loss after 12 months of storage in ambient conditions; 1100 hours under maximum power point tracking; a total ultraviolet irradiation dosage of 15 kWh m−2; and 60 thermal cycles from −40 to 85 °C.

scholarly journals Synthesis of ZnO doped high valence S element and study of photogenerated charges properties

RSC Advances ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 4422-4427 ◽  
Author(s):  
Lijing Zhang ◽  
Xiufang Zhu ◽  
Zhihui Wang ◽  
Shan Yun ◽  
Tan Guo ◽  
...  
Keyword(s):  
Uniform Distribution ◽  
Valence Band ◽  
Valence Band Maximum ◽  
Band Maximum

The uniform distribution of S dopants elevated the valence band maximum by mixing S 3p with the upper valence band states of ZnO. The valence band maxima of S–ZnO was 0.37 eV higher than that of ZnO.

Valence-band maximum in the layered semiconductor WSe2: Application of constant-energy contour mapping by photoemission

1996 ◽  
Vol 53 (24) ◽  
pp. R16152-R16155 ◽  
Author(s):  
Th. Straub ◽  
K. Fauth ◽  
Th. Finteis ◽  
M. Hengsberger ◽  
R. Claessen ◽  
...  
Keyword(s):  
Valence Band ◽  
Valence Band Maximum ◽  
Layered Semiconductor ◽  
Constant Energy ◽  
Band Maximum ◽  
Contour Mapping ◽  
Energy Contour

Effects of the band offset on interfacial deep levels

1988 ◽  
Vol 3 (1) ◽  
pp. 164-166
Author(s):  
Richard P. Beres ◽  
Roland E. Allen ◽  
John D. Dow
Keyword(s):  
Valence Band ◽  
Energy Levels ◽  
Valence Band Maximum ◽  
Deep Levels ◽  
Band Offset ◽  
Valence Band Offset ◽  
Band Maximum ◽  
Antisite Defects

The energy levels of antisite defects at a GaAs/Ge (110) interface are calculated and shown to be essentially unaltered with respect to the GaAs valence band maximum by different choices of the valence band offset.

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