scholarly journals Interface Structure and Band Alignment of CZTS/CdS Heterojunction: An Experimental and First-Principles DFT Investigation

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4040 ◽  
Author(s):  
Sachin Rondiya ◽  
Yogesh Jadhav ◽  
Mamta Nasane ◽  
Sandesh Jadkar ◽  
Nelson Y. Dzade
Keyword(s):  
Dft Calculations ◽  
First Principles ◽  
Density Functional ◽  
Rf Sputtering ◽  
Band Alignment ◽  
Charge Carriers ◽  
Band Offsets ◽  
Conduction Band Offset ◽  
Cv Measurements ◽  
Czts Thin Films

We report a phase-pure kesterite Cu2ZnSnS4 (CZTS) thin films, synthesized using radio frequency (RF) sputtering followed by low-temperature H2S annealing and confirmed by XRD, Raman spectroscopy and XPS measurements. Subsequently, the band offsets at the interface of the CZTS/CdS heterojunction were systematically investigated by combining experiments and first-principles density functional theory (DFT) calculations, which provide atomic-level insights into the nature of atomic ordering and stability of the CZTS/CdS interface. A staggered type II band alignment between the valence and conduction bands at the CZTS/CdS interface was determined from Cyclic Voltammetry (CV) measurements and the DFT calculations. The conduction and valence band offsets were estimated at 0.10 and 1.21 eV, respectively, from CV measurements and 0.28 and 1.15 from DFT prediction. Based on the small conduction band offset and the predicted higher positions of the VBmax and CBmin for CZTS than CdS, it is suggested photogenerated charge carriers will be efficient separated across the interface, where electrons will flow from CZTS to the CdS and and vice versa for photo-generated valence holes. Our results help to explain the separation of photo-excited charge carriers across the CZTS/CdS interface and it should open new avenues for developing more efficient CZTS-based solar cells.

A first-principles study on the electronic and optical properties of a type-II C2N/g-ZnO van der Waals heterostructure

2021 ◽  
Vol 23 (6) ◽  
pp. 3963-3973
Author(s):  
Jianxun Song ◽  
Hua Zheng ◽  
Minxia Liu ◽  
Geng Zhang ◽  
Dongxiong Ling ◽  
...  
Keyword(s):  
Optical Properties ◽  
Dft Calculations ◽  
First Principles ◽  
Van Der Waals ◽  
Band Alignment ◽  
Type Ii ◽  
Electronic And Optical Properties ◽  
Direct Bandgap ◽  
Van Der Waals Heterostructure ◽  
Vdw Heterostructure

The structural, electronic and optical properties of a new vdW heterostructure, C2N/g-ZnO, with an intrinsic type-II band alignment and a direct bandgap of 0.89 eV at the Γ point are extensively studied by DFT calculations.

Prediction of Beryllium Clusters from First Principles: Be17 as a Promising New Material for Water Splitting

2021 ◽  
Author(s):  
Behnaz Abyaz ◽  
Zabiollah Mahdavifar ◽  
Georg Schreckenbach ◽  
Yang Gao
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Water Splitting ◽  
First Principles ◽  
Density Functional ◽  
Global Minimum ◽  
Functional Theory ◽  
New Material ◽  
Universal Structure

Evolutionary searches using the USPEX method (Universal Structure Predictor: Evolutionary Xtallography) combined with density functional theory (DFT) calculations were performed to obtain the global minimum structures of beryllium (Ben, n=3-25)...

Low-dimensional HfS2 as SO2 adsorbent and gas sensor: Effect of water and sulfur vacancies

2021 ◽  
Author(s):  
Amina Bouheddadj ◽  
Tarik Ouahrani ◽  
Gbèdodé Wilfried KANNHOUNON ◽  
Boufatah Reda ◽  
Sumeya Bedrane ◽  
...  
Keyword(s):  
Climate Change ◽  
Density Functional Theory ◽  
Dft Calculations ◽  
Gas Sensor ◽  
First Principles ◽  
Density Functional ◽  
Two Dimensional ◽  
Functional Theory ◽  
Sensor Effect ◽  
Low Dimensional

First-principles based on density functional theory (DFT) calculations were performed to investigate the interaction of two-dimensional (2D) HfS2 with SO2, a harmful gas with implications for climate change. In particular,...

scholarly journals First–Principles Investigation of the Structural, Elastic, Electronic, and Optical Properties of α– and β–SrZrS3: Implications for Photovoltaic Applications

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 978
Author(s):  
Henry Igwebuike Eya ◽  
Esidor Ntsoenzok ◽  
Nelson Y. Dzade
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Visible Region ◽  
Charge Carriers ◽  
Band Gaps ◽  
Strong Light ◽  
Electronic And Optical Properties ◽  
Optical Absorbance ◽  
Effective Masses

Transition metal perovskite chalcogenides are attractive solar absorber materials for renewable energy applications. Herein, we present the first–principles screened hybrid density functional theory analyses of the structural, elastic, electronic and optical properties of the two structure modifications of strontium zirconium sulfide (needle–like α–SrZrS3 and distorted β–SrZrS3 phases). Through the analysis of the predicted electronic structures, we show that both α– and β–SrZrS3 materials are direct band gaps absorbers, with calculated band gaps of 1.38, and 1.95 eV, respectively, in close agreement with estimates from diffuse–reflectance measurements. A strong light absorption in the visible region is predicted for the α– and β–SrZrS3, as reflected in their high optical absorbance (in the order of 105 cm−1), with the β–SrZrS3 phase showing stronger absorption than the α–SrZrS3 phase. We also report the first theoretical prediction of effective masses of photo-generated charge carriers in α– and β–SrZrS3 materials. Predicted small effective masses of holes and electrons at the valence, and conduction bands, respectively, point to high mobility (high conductivity) and low recombination rate of photo-generated charge carriers in α– and β–SrZrS3 materials, which are necessary for efficient photovoltaic conversion.

A first principles study of H2S adsorption and decomposition on a Ge(100) surface

RSC Advances ◽  
2015 ◽  
Vol 5 (5) ◽  
pp. 3825-3832 ◽  
Author(s):  
Tsung-Fan Teng ◽  
Santhanamoorthi Nachimuthu ◽  
Wei-Hsiu Hung ◽  
Jyh-Chiang Jiang
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
First Principles ◽  
Density Functional ◽  
Reaction Paths ◽  
Functional Theory ◽  
First Principles Study ◽  
H2s Adsorption

We employed density functional theory (DFT) calculations to examine the adsorption configurations and possible reaction paths for H2S on a Ge(100) surface.

Experimental and First-Principles Studies of the Band Alignment at the HfO2/4H-SiC (0001) Interface

2006 ◽  
Vol 527-529 ◽  
pp. 1071-1074 ◽  
Author(s):  
Carey M. Tanner ◽  
Jong Woo Choi ◽  
Jane P. Chang
Keyword(s):  
Conduction Band ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Atomic Layer ◽  
Band Alignment ◽  
Functional Theory ◽  
X Ray ◽  
Conduction Band Offset ◽  
Mos Devices ◽  
Layer Deposition

The electronic properties of HfO2 films on 4H-SiC were investigated to determine their suitability as high-κ dielectrics in SiC power MOS devices. The band alignment at the HfO2/4HSiC interface was determined by X-ray photoelectron spectroscopy (XPS) and supported by density functional theory (DFT) calculations. For the experimental study, HfO2 films were deposited on ntype 4H-SiC by atomic layer deposition (ALD). XPS analysis yielded valence and conduction band offsets of 1.69 eV and 0.75 eV, respectively. DFT predictions based on two monoclinic HfO2/4HSiC (0001) structures agree well with this result. The small conduction band offset suggests the potential need for further interface engineering and/or a buffer layer to minimize electron injection into the gate oxide.

Experimental and theoretical investigations of selenium nuclear magnetic shielding tensors in Se–N heterocycles

2009 ◽  
Vol 87 (10) ◽  
pp. 1546-1564 ◽  
Author(s):  
Andre Sutrisno ◽  
Andy Y.H. Lo ◽  
Joel A. Tang ◽  
Jason L. Dutton ◽  
Gregg J. Farrar ◽  
...  
Keyword(s):  
Dft Calculations ◽  
First Principles ◽  
Density Functional ◽  
Molecular Geometry ◽  
Molecular Structures ◽  
Magnetic Shielding ◽  
First Principles Calculations ◽  
Theoretical Investigations ◽  
Intermolecular Contacts ◽  
Nuclear Magnetic

A preliminary study involving solid-state 77Se NMR spectroscopy and first principles calculations of 77Se NMR parameters in Se–N heterocycles is reported. 77Se CP/MAS NMR spectra of the ring systems reveal expansive selenium chemical shift (CS) tensors, which are extremely sensitive to molecular geometry, symmetry, ligand substitution, and intermolecular contacts. For systems with known crystal structures, hybrid density functional theory (DFT) calculations of selenium nuclear magnetic shielding (NMS) tensors were carried out, and tensor orientations in the molecular frames examined. Additional DFT calculations of selenium NMS tensors are presented, along with a detailed analysis of pairs of occupied and virtual molecular orbitals that give rise to the Se NMS tensors. A new naturalized local molecular orbital (NLMO) analysis under the same DFT framework is also discussed. Collectively, the NMR data and first principles calculations provide understanding of the influences of electronic structure, bonding, and intermolecular interactions on the selenium NMS tensors, allowing for (i) prediction of unknown molecular structures and (ii) insight into the positions of the stereochemically active selenium lone pairs.

Band-gap tuning of graphene by Be doping and Be, B co-doping: a DFT study

RSC Advances ◽  
2015 ◽  
Vol 5 (69) ◽  
pp. 55762-55773 ◽  
Author(s):  
Saif Ullah ◽  
Akhtar Hussain ◽  
WaqarAdil Syed ◽  
Muhammad Adnan Saqlain ◽  
Idrees Ahmad ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Co Doping ◽  
Structural And Electronic Properties ◽  
Doped Graphene ◽  
Band Gap Tuning ◽  
Co Doped

First-principles density functional theory (DFT) calculations were carried out to investigate the structural and electronic properties of beryllium (Be) doped and, Be with boron (B) co-doped graphene systems.

Structure-activity relationships in the production of olefins from alcohols and ethers: a first-principles theoretical study

2015 ◽  
Vol 5 (9) ◽  
pp. 4547-4555 ◽  
Author(s):  
Pavlo Kostetskyy ◽  
Giannis Mpourmpakis
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Lewis Acid ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Study ◽  
Functional Theory ◽  
Structure Activity Relationships ◽  
Structure Activity

Olefin formation pathways on Lewis acid (LA) sites of Al2O3, Ga2O3 and In2O3 and gallium- and indium-doped alumina were investigated using Density Functional Theory (DFT) calculations.

Defect-Pairs of Titanium and Carbon in Iron Oxide Film for Efficient Visible Light Driven Water Splitting

2018 ◽  
Vol MA2018-01 (31) ◽  
pp. 1910-1910
Author(s):  
Il Yong Choi ◽  
Donghun Kim ◽  
Tae Hwa Jeon ◽  
Byeong-Gyu Chae ◽  
Kug-Seung Lee ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Electrical Properties ◽  
Visible Light ◽  
Water Splitting ◽  
Density Functional ◽  
Photocurrent Density ◽  
Band Alignment ◽  
Charge Carriers ◽  
Charge Carrier Density ◽  
Pec Water Splitting

Solar-powered photoelectrochemical (PEC) water splitting has been a promising candidate for producing hydrogen in a clean and renewable way. Photoelectrodes are key components in PEC cells for efficient and stable hydrogen generation because they play crucial roles in absorption of photons, the separation and transportation of photo-generated charge carriers, as well as the chemical reactions with water. A variety of metal oxides for efficient photoelectrode have been intensively explored, but it is still challenging to find desirable materials to satisfy lots of requirements for PEC water splitting. Iron oxide (hematite, Fe2O3) has recently attracted much attention due to its earth abundance, low cost as well as desirable material properties for PEC water oxidation including narrow band gap energy of 2.0~2.2eV for visible light absorption and proper energy band alignment, etc. However, Fe2O3 has very short hole diffusion length and low carrier mobility, which causes considerable recombination of photo-generated electrons and holes. A lot of approaches such as nanostructures, heterojunction with other materials, surface modification, etc. have been reported to prevent the recombination of charge carriers and improve electrical properties of Fe2O3; however, these require complex manufacturing processes. In the present work, we found a much simpler way to improve the electrical properties of Fe2O3 film, namely defect-pairs due to co-doping. Titanium (Ti) and carbon (C) co-doped thin Fe2O3 film (i.e. (Ti,C)-Fe2O3) has been realized via a combination of simple solution-based spin-coating and tube furnace annealing process. This film turns out to lead significantly enhanced PEC performance when used as a photoanode: an impressively high photocurrent density of more than 4.5mAcm-2 was achieved at 1.23VRHE under AM1.5G solar spectrum and 1 sun illumination. This is compared to the value of Ti-doped Fe2O3 film, which is only about 2.6mAcm-2 photocurrent density at 1.23VRHE even though the optical properties of each film are similar. The origin for such substantial enhancement was revealed using a series of experimental and computational spectroscopies. X-ray absorption spectroscopy, electrochemical impedance measurements and density-functional-theory calculations both indicate that C atoms can be more deeply and heavily doped under the existence of Ti dopants in Fe2O3 film and then the defect-pairs of Ti and C increase not only charge carrier density but also electron’s mobility. An emphasis should be placed on the fact that this achievement was not assisted by co-catalysts and complex nanostructuring methods; hence even higher performance is expected when the film is further treated with extra-cares.

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