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.

Theoretical Investigation on Electronic Properties of ZnO Crystals Using DFT-Based Calculation Method

2015 ◽  
Vol 1112 ◽  
pp. 41-44 ◽  
Author(s):  
Yudi Darma ◽  
Freddy Giovanni Setiawan ◽  
Muhammad Aziz Majidi ◽  
Andrivo Rusydi
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Valence Band Maximum ◽  
Band Gaps ◽  
Generalized Gradient ◽  
Strong Electron ◽  
Electronic Band ◽  
Rocksalt Structure

We study the electronic band structure and density of states (DOS) on ZnO material in various crystal structures : wurtzite (W), zincblende (ZB), and rocksalt (RS) phases. Calculations are based on Density Functional Theory (DFT) with Generalized Gradient Approximation (GGA) for exchange-correlation functional and Hubbard correction to consider the strong electron correlations in 3d orbitals. After structural optimization, GGA results show that wurtzite and zincblende structures have a direct band gap of 0.749 eV and 0.637 eV, respectively, whereas rocksalt structure has an indirect band gap of 0.817 eV. Symmetrical shape of total DOS for spin up and spin down electrons indicates a zero total magnetic moment. For all ZnO structures, the upper valence band is formed by hybridization among O 2p and Zn 3d orbitals, while lower valence and conduction band are primarily filled by O 2s and Zn 4s, respectively. The GGA+U approach is found to improve the calculated band gaps and correct the position of Zn 3d state below Valence Band Maximum (VBM). From GGA+U, the band gaps for W-ZnO, ZB-ZnO, and RS-ZnO are 1.12 eV, 1.00 eV, and 1.11 eV, respectively.

scholarly journals (112) Surface of CuInSe2Thin Films with Doped Cd Atoms

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Bo Yin ◽  
Chaogang Lou
Keyword(s):  
Thin Films ◽  
Electronic Structure ◽  
Valence Band ◽  
Electronic Structures ◽  
Formation Energy ◽  
Valence Band Maximum ◽  
Band Maximum ◽  
Doping Behavior

The doping behavior of Cd atoms in the CuInSe2thin films and their influences on electronic structures are investigated. The doped Cd atoms replace Cu atoms and prefer to stay at the (112) surface of the thin films. They combine with Cu vacancies to form defect pairs due to low formation energy. The Cd atom does not by itself modify significantly the electronic structure of the surface, but the defect pairs have important influences. They result in a down shift of valence band maximum and form a hole barrier at the surface, which can prevent holes from reaching the surface and reduce the recombination of carriers.

The “electron crystal” behavior in copper chalcogenides Cu2X (X = Se, S)

2017 ◽  
Vol 5 (10) ◽  
pp. 5098-5105 ◽  
Author(s):  
Yongxing Sun ◽  
Lili Xi ◽  
Jiong Yang ◽  
Lihua Wu ◽  
Xun Shi ◽  
...  
Keyword(s):  
Transport Properties ◽  
Valence Band ◽  
Electronic Structures ◽  
Electrical Transport ◽  
Valence Band Maximum ◽  
Electrical Transport Properties ◽  
Band Maximum ◽  
Copper Chalcogenides ◽  
Structural Fluctuation ◽  
Electron Crystal

In Cu2Se, the structural fluctuation of the Cu sites have minor effects on the electronic structures around valence band maximum. The electrical transport properties of Cu2Se are mainly determined by the Se sublattice; Cu atoms serve as the carrier reservoirs.

Electronic Structures of P-Type Doped CuInS2

1996 ◽  
Vol 426 ◽  
Author(s):  
T. Yamamoto ◽  
H. Katayama-Yoshida
Keyword(s):  
Electronic Structures ◽  
Electronic Band Structure ◽  
Spherical Wave ◽  
Material Design ◽  
Electronic Band ◽  
Design Considerations ◽  
Band Structure Calculations ◽  
P Type ◽  
Structure Calculations ◽  
Codoping Method

AbstractWe have studied the electronic structures of CuIn(S0.875X0.125)2 (X=B, C, N, Si or P) based on the ab-initio electronic band structure calculations using the augmented spherical wave (ASW) method. We have clarified that the physical characteristics of the p-type doped CuInS2 crystals are mainly determined by a change in the strength of interactions between Cu and S atoms. On the basis of the calculated results, we discussed the material design considerations, such as controlling the strength of resistivity for p-type doped CulnS2 materials and converting the conduction type, from n-type to p-type by a codoping method.

Co-doping of magnesium with indium in nitrides: first principle calculation and experiment

RSC Advances ◽  
2016 ◽  
Vol 6 (6) ◽  
pp. 5111-5115 ◽  
Author(s):  
Zhiqiang Liu ◽  
Binglei Fu ◽  
Xiaoyan Yi ◽  
Guodong Yuan ◽  
Junxi Wang ◽  
...  
Keyword(s):  
Valence Band ◽  
Valence Band Maximum ◽  
First Principle ◽  
Principle Calculation ◽  
First Principle Calculation ◽  
Band Maximum ◽  
Co Doping ◽  
P Type

The valence band maximum could be modified by specific states coupling, thus improving the p-type dopability in In–Mg co-doping GaN.

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.

scholarly journals Attosecond intra-valence band dynamics and resonant-photoemission delays in W(110)

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
S. Heinrich ◽  
T. Saule ◽  
M. Högner ◽  
Y. Cui ◽  
V. S. Yakovlev ◽  
...  
Keyword(s):  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Electronic Band Structure ◽  
Photoelectric Effect ◽  
Final State ◽  
Electronic Band ◽  
Time Resolved ◽  
Resonant Photoemission ◽  
Pulse Trains ◽  
Electron Correlation Effects

AbstractTime-resolved photoelectron spectroscopy with attosecond precision provides new insights into the photoelectric effect and gives information about the timing of photoemission from different electronic states within the electronic band structure of solids. Electron transport, scattering phenomena and electron-electron correlation effects can be observed on attosecond time scales by timing photoemission from valence band states against that from core states. However, accessing intraband effects was so far particularly challenging due to the simultaneous requirements on energy, momentum and time resolution. Here we report on an experiment utilizing intracavity generated attosecond pulse trains to meet these demands at high flux and high photon energies to measure intraband delays between sp- and d-band states in the valence band photoemission from tungsten and investigate final-state effects in resonant photoemission.

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 Analyzing transport properties of p-type Mg2Si–Mg2Sn solid solutions: optimization of thermoelectric performance and insight into the electronic band structure

2019 ◽  
Vol 7 (3) ◽  
pp. 1045-1054 ◽  
Author(s):  
Hasbuna Kamila ◽  
Prashant Sahu ◽  
Aryan Sankhla ◽  
Mohammad Yasseri ◽  
Hoang-Ngan Pham ◽  
...  
Keyword(s):  
Band Structure ◽  
Transport Properties ◽  
Carrier Concentration ◽  
Solid Solutions ◽  
Figure Of Merit ◽  
Electronic Band Structure ◽  
Thermoelectric Performance ◽  
Electronic Band ◽  
P Type ◽  
Insight Into

Figure of merit zT mapping of p-Mg2Si1−xSnx with respect to carrier concentration.

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.

Sign in / Sign up

Export Citation Format

Share Document