scholarly journals Effect of Copper Doping on Electronic Structure and Optical Absorption of Cd33Se33 Quantum Dots

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2531
Author(s):  
Fengai Zhao ◽  
Shuanglin Hu ◽  
Canhui Xu ◽  
Haiyan Xiao ◽  
Xiaosong Zhou ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Oxidation State ◽  
Density Functional ◽  
High Efficiency ◽  
Photophysical Properties ◽  
Visible Region ◽  
Transition Metal Ions ◽  
Cdse Qds ◽  
Hybrid Functional

The photophysical properties of Cu-doped CdSe quantum dots (QDs) can be affected by the oxidation state of Cu impurity, but disagreement still exists on the Cu oxidation state (+1 or +2) in these QDs, which is debated and poorly understood for many years. In this work, by using density functional theory (DFT)-based calculations with the Heyd–Scuseria–Ernzerhof (HSE) screened hybrid functional, we clearly demonstrate that the incorporation of Cu dopants into the surface of the magic sized Cd33Se33 QD leads to non-magnetic Cu 3d orbitals distribution and Cu+1 oxidation state, while doping Cu atoms in the core region of QDs can lead to both Cu+1 and Cu+2 oxidation states, depending on the local environment of Cu atoms in the QDs. In addition, it is found that the optical absorption of the Cu-doped Cd33Se33 QD in the visible region is mainly affected by Cu concentration, while the absorption in the infrared regime is closely related to the oxidation state of Cu. The present results enable us to use the doping of Cu impurity in CdSe QDs to achieve special photophysical properties for their applications in high-efficiency photovoltaic devices. The methods used here to resolve the electronic and optical properties of Cu-doped CdSe QDs can be extended to other II-VI semiconductor QDs incorporating transition-metal ions with variable valence.

scholarly journals Tuning the optoelectronic properties of hematite with rhodium doping for photoelectrochemical water splitting using density functional theory approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abdur Rauf ◽  
Muhammad Adil ◽  
Shabeer Ahmad Mian ◽  
Gul Rahman ◽  
Ejaz Ahmed ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Optical Absorption ◽  
Water Splitting ◽  
Density Functional ◽  
Formation Energy ◽  
Visible Region ◽  
Photoelectrochemical Water Splitting ◽  
Theory Approach ◽  
Functional Theory

AbstractHematite (Fe2O3) is one of the best candidates for photoelectrochemical water splitting due to its abundance and suitable bandgap. However, its efficiency is mostly impeded due to the intrinsically low conductivity and poor light absorption. In this study, we targeted this intrinsic behavior to investigate the thermodynamic stability, photoconductivity and optical properties of rhodium doped hematite using density functional theory. The calculated formation energy of pristine and rhodium doped hematite was − 4.47 eV and − 5.34 eV respectively, suggesting that the doped material is thermodynamically more stable. The DFT results established that the bandgap of doped hematite narrowed down to the lower edge (1.61 eV) in the visible region which enhanced the optical absorption and photoconductivity of the material. Moreover, doped hematite has the ability to absorb a broad spectrum (250–800) nm. The enhanced optical absorption boosted the photocurrent and incident photon to current efficiency. The calculated results also showed that the incorporation of rhodium in hematite induced a redshift in optical properties.

Theoretical investigation on the photocatalytic activity of the Au/g-C3N4 monolayer

2017 ◽  
Vol 16 (02) ◽  
pp. 1750013 ◽  
Author(s):  
Guoyan Nie ◽  
Peng Li ◽  
Jin-Xia Liang ◽  
Chun Zhu
Keyword(s):  
Optical Properties ◽  
Photocatalytic Activity ◽  
Density Functional ◽  
High Stability ◽  
Carbon Nitride ◽  
Visible Region ◽  
Single Layer ◽  
Single Atom ◽  
Two Dimensional ◽  
Hybrid Functional

Two-dimensional optical catalysis materials have a wonderful potential application. Here, a new two-dimensional material consisting of the supported single-atom Au on a graphite carbon nitride (g-C3N[Formula: see text] single layer has been designed and its electronic and optical properties have been characterized by density functional calculations. The bandgap of 1.82[Formula: see text]eV calculated by the hybrid functional HSE06 shows that the Au/g-C3N4 is an indirect semiconductor, and the electron can easily be excited from the single-atom Au to the bottom of the conduction band. This material therefore has relatively strong optical properties in the visible region. Moreover, the process of Au insertion into the cavity of g-C3N4 single layer is energy-favorable. This work may provide insights and a new avenue for fabricating supported Au catalysts with high stability.

Light-driven hydrogen production with CdSe quantum dots and a cobalt glutathione catalyst

2021 ◽  
Vol 57 (16) ◽  
pp. 2053-2056
Author(s):  
Rebeckah Burke ◽  
Saikat Chakraborty ◽  
Kevin P. McClelland ◽  
Jana Jelušić ◽  
Ellen M. Matson ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Hydrogen Production ◽  
Cobalt Catalyst ◽  
High Efficiency ◽  
Cdse Quantum Dots ◽  
Cdse Qds ◽  
Photocatalytic System

A robust photocatalytic system with CdSe QDs and a molecular cobalt catalyst produces H2 with high efficiency and activity.

scholarly journals Electronic characteristics of CdS quantum dots with defects

2020 ◽  
pp. 28
Author(s):  
I. M. Kupchak ◽  
D. V. Korbutyak ◽  
N. F. Serpak
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Valence Band ◽  
Absorption Spectra ◽  
Density Functional ◽  
Optical Absorption Spectra ◽  
Cds Quantum Dots ◽  
Generalized Gradient ◽  
Substitutional Impurity ◽  
Cadmium Vacancy

Using the density functional theory and the generalized gradient approximation, we calculated the atomic structure, the density of electronic states, and the optical absorption spectra of CdS quantum dots containing intrinsic defects — a cadmium vacancy VCd and an interstitial sulfur atom SI, and substitutional impurities — zinc and copper in place of the atom cadmium — ZnCd and CuCd, respectively. The calculations were performed for the Cd33S33 cluster corresponding to the so-called “magic” size of the quantum dot. This size has a minimum of dangling bonds at the surface and allows the using of such a cluster without the passivation. The structural relaxation during the formation of such defects and the distribution of the wave function of the state corresponding to the top of the valence band are analyzed in details. It has been shown that the cadmium vacancy forms local states in the band gap of CdS nanocrystals, and can serve as centers of radiative recombination. Other defects form energy levels in the depths of the valence band or near its top, but whose energy positions do not correspond to the band maxima in the experimental photoluminescence spectra of CdS quantum dots, both undoped and doped with zinc. The calculated optical absorption spectra demonstrate a strong peak in the region of fundamental absorption of CdS for a cluster containing a substitutional impurity of CuCd, in contrast to other systems where no such peaks are observed. In addition, the replacement of the cadmium atom with copper leads to a decrease in the number of chemical bonds to three and, accordingly, to the largest relaxation among the systems studied. This feature is caused by the crystal structure inhomogeneity of copper sulfide CuxS, which, depending on stoichiometry, can be either a semiconductor or a metal.

Variations in the optical properties of TiO2 with Pb doping using ab initio calculations

2021 ◽  
Author(s):  
Hamid Khan ◽  
Yaseen Iqbal ◽  
Matiullah Khan ◽  
S. N. Ahmad ◽  
Yi Zeng
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Density Functional ◽  
Separation Efficiency ◽  
Computational Study ◽  
Visible Region ◽  
Solar Spectrum ◽  
High Rate ◽  
Practical Applications ◽  
Pb Doping

Titanium dioxide (TiO2) is one of the most promising photocatalysts for photoelectrochemical applications due to its high chemical as well as photochemical stability. Its efficiency in practical applications is limited due to its wide bandgap, a high rate of recombination of electron–hole pairs and the weak photo-carriers separation efficiency. In this computational study, a path was followed to find out the redshift of the TiO2 light absorption edge via lead (Pb) doping. The density functional theory (DFT) results revealed that the doped TiO2 bandgap was decreased to the lower edge (2.1 eV) in the visible region resulting in a relatively better optical absorption of the material. Furthermore, doped TiO2 was found to absorb a large part of the solar spectrum. The improvement in optical absorption resulted in good photo response. The calculated results also showed a redshift in optical properties produced through the doping of Pb in TiO2.

Tuning Optoelectronic Properties of 4H-SiC QDs Using -H, -OH and -F Surface Functionalisation

2015 ◽  
Vol 821-823 ◽  
pp. 375-378 ◽  
Author(s):  
Marzaini Rashid ◽  
Amit Kumar Tiwari ◽  
Neal Wood ◽  
Patrick Briddon ◽  
Jonathan P. Goss ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Quantum Confinement ◽  
Density Functional ◽  
Size Dependent ◽  
Optical Gap ◽  
Quantum Confinement Effects ◽  
Similar Cluster ◽  
Homo And Lumo ◽  
Surface Functionalisation

Density functional calculations were performed for the –H, –OH and –F functional groups adsorbed onto the surface of pseudo-spherical 4H-SiC quantum dots with diameters ranging from 10 to 22 Å. We find that for the investigated diameter range, the H-terminated SiC-quantum dots exhibit strong size dependent quantum confinement effects, while for –F and –OH terminations, the optical gap remains largely unchanged. The –H termination shows an optical absorption onset well above that of –F and –OH for a similar cluster size, which is attributed to the localisation of HOMO and LUMO states to the quantum dot core. Based on our calculations, we suggest that the –H functionalisation is a more promising route for engineering the optical properties of SiC-quantum dots, since this could lead to a wider control over the optical absorption onsets, when compared to –OH and –F terminations.

scholarly journals Photophysical Properties of Multilayer Graphene–Quantum Dots Hybrid Structures

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 714 ◽  
Author(s):  
Ivan Reznik ◽  
Andrey Zlatov ◽  
Mikhail Baranov ◽  
Roman Zakoldaev ◽  
Andrey Veniaminov ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Energy Transfer ◽  
Average Rate ◽  
Photophysical Properties ◽  
Graphene Quantum Dots ◽  
Hybrid Structures ◽  
Multilayer Graphene ◽  
Cdse Qds ◽  
Efficient Charge ◽  
Photoinduced Processes

Photoelectrical and photoluminescent properties of multilayer graphene (MLG)–quantum dots (QD) hybrid structures have been studied. It has been shown that the average rate of transfer from QDs to the MLG can be estimated via photoinduced processes on the QDs’ surfaces. A monolayer of CdSe QDs can double the photoresponse amplitude of multilayer graphene, without influencing its characteristic photoresponse time. It has been found that efficient charge or energy transfer from QDs to MLG with a rate higher than 3 × 108 s−1 strongly inhibits photoinduced processes on the QD surfaces and provides photostability for QD-based structures.

Photo-Electrochemical Water Splitting Behavior of Directionally Aligned CdSe Quantum Dots on Copper(II) Benzene-1,3,5-Tricarboxylate Metal-Organic Frameworks (MOFs)

2021 ◽  
Vol 21 (3) ◽  
pp. 1623-1635
Author(s):  
Anup Kuchipudi ◽  
S. Suresh Reddy ◽  
S. Vengatesan ◽  
Subhendu K. Panda ◽  
Gosipathala Sreedhar
Keyword(s):  
Quantum Dots ◽  
Water Splitting ◽  
Light Harvesting ◽  
Metal Organic Frameworks ◽  
Visible Region ◽  
Cdse Quantum Dots ◽  
Cdse Qds ◽  
Broad Absorption Band ◽  
Metal Organic ◽  
Electrochemical Water Splitting

Herein, a facile synthesis protocol for the development of directional alignment of CdSe quantum dots (QDs) on the surface of Copper benzene-1, 3, 5-tricarboxylate (CuBTC) metal-organic frameworks (MOFs) was proposed. The sensitization of CdSe QDs with MOFs offered enhancement of light-harvesting properties in the visible region of the solar spectrum due to the broad absorption band of CdSe QDs. As a photo-anode, it has generated current density of ˜20 mA/cm2 at 1.70 V (vs. Reversible hydrogen electrode (RHE)) during the photo-electrochemical water splitting in 1 M Na2S electrolyte. The present investigation demonstrates the directional attachment of CdSe QDs on CuBTC is beneficial in facilitating light-harvesting and photo-electrochemical properties of CuBTC MOFs.

scholarly journals Modification of NFA-Conjugated Bridges with Symmetric Structures for High-Efficiency Non-Fullerene PSCs

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 958 ◽  
Author(s):  
Qiuchen Lu ◽  
Ming Qiu ◽  
Meiyu Zhao ◽  
Zhuo Li ◽  
Yuanzuo Li
Keyword(s):  
Optical Absorption ◽  
Density Functional ◽  
High Efficiency ◽  
Polymer Solar Cells ◽  
Open Circuit ◽  
Functional Theory ◽  
Photoelectric Properties ◽  
Voltage Loss ◽  
Td Dft ◽  
Symmetric Structures

As electron acceptors, non-fullerene molecules can overcome the shortcomings of fullerenes and their derivatives (such as high cost, poor co-solubility, and weak light absorption). The photoelectric properties of two potential non-fullerene polymer solar cells (PSCs) PBDB-T:IF-TN (PB:IF) and PBDB-T:IDT-TN (PB:IDT) are studied by density functional theory (DFT) and time-dependent DFT (TD-DFT). Based on the optimized structure of the ground state, the effects of the electron donor (D) and electron acceptor (A) (D/A) interfaces PBDB-T/IF-TN (PB/IF) and PBDB-T/IDT-TN (PB/IDT) are studied by a quantum-chemical method (QM) and Marcus theory. Firstly, for two non-fullerene acceptors (NFAs) IF-TN and IDT-TN, the NFA IDT-TN has better optical absorption ability and better electron transport ability than IF-TN. Secondly, for the D/A interfaces PB/IF and PB/IDT, they both have high optical absorption and electron transfer abilities, and PB/IDT has better optical absorption and lower exciton binding energy. Finally, some important parameters (open-circuit voltage, voltage loss, fill factor, and power conversion efficiency) are calculated and simulated by establishing the theoretical model. From the above analysis, the results show that the non-fullerene PSC PB:IDT has better photoelectric characteristics than PB:IF.

scholarly journals A theoretical study on photo absorption in silicon decorated boron clusters (BnSi, n=7-10)

2021 ◽  
Vol 2070 (1) ◽  
pp. 012051
Author(s):  
Ankita Jaiswal ◽  
Shakti S Ray ◽  
Sridhar Sahu
Keyword(s):  
Optical Absorption ◽  
Oscillator Strength ◽  
Absorption Spectra ◽  
Density Functional ◽  
Visible Region ◽  
Basis Set ◽  
Functional Study ◽  
Strength Analysis ◽  
Optical Absorption Spectra ◽  
Boron Clusters

Abstract In this work, we have studied the optical absorption spectra of small boron clusters doped with single silicon atom (BnSi, n=7-10) and is reported employing CAM-B3LYP functional with 6-311+G(d) basis –set within the framework of time dependent density functional study (TD-DFT). We have computed excitation energy, oscillator strength, wavelength and the corresponding orbital transitions associated with a given oscillator strength. Analysis of optical absorption spectra of studied clusters shows that most of the absorption peaks are found in the ultraviolet-visible (UV-Vis) region (200 nm-700 nm). The major peaks are found to fall in UV region along with some weaker peaks at visible region. The most intense peak is recorded for B8Si cluster at 232 nm and oscillator strength of 0.084. This peak is associated with the orbital transition from H-4→L+1.

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