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Dong X, Wang T, Lu Z, An Y, Wang Y. Computational design of a reliable intermediate-band photovoltaic absorber based on diamond. OPTICS EXPRESS 2023; 31:18227-18239. [PMID: 37381537 DOI: 10.1364/oe.491398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 05/04/2023] [Indexed: 06/30/2023]
Abstract
To reduce the wide bandgap of diamond and expand its applications in the photovoltaic fields, a diamond-based intermediate-band (IB) material C-Ge-V alloy was designed by first-principles calculations. By replacing some C with Ge and V in the diamond, the wide bandgap of the diamond can be reduced sharply and a reliable IB, which is mainly formed by the d states of V, can be formed in the bandgap. With the increase of Ge content, the total bandgap of the C-Ge-V alloy will be reduced and close to the optimal value of an IB material. At a relatively low atomic concentration of Ge (below 6.25%), the IB formed in the bandgap is partially filled and varies little with the concentration of Ge. When further increasing the content of Ge, the IB moves close to the conduction band and the electron filling in the IB increases. The 18.75% content of Ge might be the limitation to form an IB material, and the optimal content of Ge should be between 12.5% and 18.75%. Compared with the content of Ge, the distribution of Ge has a minor effect on the band structure of the material. The C-Ge-V alloy shows strong absorption for the sub-bandgap energy photons, and the absorption band generates a red-shift with the increase of Ge. This work will further expand the applications of diamond and be helpful to develop an appropriate IB material.
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Cuadra L, Salcedo-Sanz S, Nieto-Borge JC. Carrier Transport in Colloidal Quantum Dot Intermediate Band Solar Cell Materials Using Network Science. Int J Mol Sci 2023; 24:3797. [PMID: 36835214 PMCID: PMC9960920 DOI: 10.3390/ijms24043797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 02/05/2023] [Accepted: 02/08/2023] [Indexed: 02/17/2023] Open
Abstract
Colloidal quantum dots (CQDs) have been proposed to obtain intermediate band (IB) materials. The IB solar cell can absorb sub-band-gap photons via an isolated IB within the gap, generating extra electron-hole pairs that increase the current without degrading the voltage, as has been demonstrated experimentally for real cells. In this paper, we model the electron hopping transport (HT) as a network embedded in space and energy so that a node represents the first excited electron state localized in a CQD while a link encodes the Miller-Abrahams (MA) hopping rate for the electron to hop from one node (=state) to another, forming an "electron-HT network". Similarly, we model the hole-HT system as a network so that a node encodes the first hole state localized in a CQD while a link represents the MA hopping rate for the hole to hop between nodes, leading to a "hole-HT network". The associated network Laplacian matrices allow for studying carrier dynamics in both networks. Our simulations suggest that reducing both the carrier effective mass in the ligand and the inter-dot distance increases HT efficiency. We have found a design constraint: It is necessary for the average barrier height to be larger than the energetic disorder to not degrade intra-band absorption.
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Affiliation(s)
- Lucas Cuadra
- Department of Signal Processing and Communications, University of Alcalá, 28805 Madrid, Spain
- Department of Physics and Mathematics, University of Alcalá, 28805 Madrid, Spain
| | - Sancho Salcedo-Sanz
- Department of Signal Processing and Communications, University of Alcalá, 28805 Madrid, Spain
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Cuadra L, Nieto-Borge JC. Approaching Disordered Quantum Dot Systems by Complex Networks with Spatial and Physical-Based Constraints. NANOMATERIALS 2021; 11:nano11082056. [PMID: 34443887 PMCID: PMC8400585 DOI: 10.3390/nano11082056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 07/22/2021] [Accepted: 08/03/2021] [Indexed: 01/01/2023]
Abstract
This paper focuses on modeling a disordered system of quantum dots (QDs) by using complex networks with spatial and physical-based constraints. The first constraint is that, although QDs (=nodes) are randomly distributed in a metric space, they have to fulfill the condition that there is a minimum inter-dot distance that cannot be violated (to minimize electron localization). The second constraint arises from our process of weighted link formation, which is consistent with the laws of quantum physics and statistics: it not only takes into account the overlap integrals but also Boltzmann factors to include the fact that an electron can hop from one QD to another with a different energy level. Boltzmann factors and coherence naturally arise from the Lindblad master equation. The weighted adjacency matrix leads to a Laplacian matrix and a time evolution operator that allows the computation of the electron probability distribution and quantum transport efficiency. The results suggest that there is an optimal inter-dot distance that helps reduce electron localization in QD clusters and make the wave function better extended. As a potential application, we provide recommendations for improving QD intermediate-band solar cells.
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Affiliation(s)
- Lucas Cuadra
- Department of Signal Processing and Communications, University of Alcalá, 28801 Alcalá de Henares, Spain
- Department of Physics and Mathematics, University of Alcalá, 28801 Alcalá de Henares, Spain;
- Correspondence:
| | - José Carlos Nieto-Borge
- Department of Physics and Mathematics, University of Alcalá, 28801 Alcalá de Henares, Spain;
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Cuadra L, Nieto-Borge JC. Modeling Quantum Dot Systems as Random Geometric Graphs with Probability Amplitude-Based Weighted Links. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:375. [PMID: 33540687 PMCID: PMC7912992 DOI: 10.3390/nano11020375] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/18/2021] [Accepted: 01/27/2021] [Indexed: 12/28/2022]
Abstract
This paper focuses on modeling a disorder ensemble of quantum dots (QDs) as a special kind of Random Geometric Graphs (RGG) with weighted links. We compute any link weight as the overlap integral (or electron probability amplitude) between the QDs (=nodes) involved. This naturally leads to a weighted adjacency matrix, a Laplacian matrix, and a time evolution operator that have meaning in Quantum Mechanics. The model prohibits the existence of long-range links (shortcuts) between distant nodes because the electron cannot tunnel between two QDs that are too far away in the array. The spatial network generated by the proposed model captures inner properties of the QD system, which cannot be deduced from the simple interactions of their isolated components. It predicts the system quantum state, its time evolution, and the emergence of quantum transport when the network becomes connected.
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Affiliation(s)
- Lucas Cuadra
- Department of Signal Processing and Communications, University of Alcalá, 28801 Alcalá de Henares, Spain
- Department of Physics and Mathematics, University of Alcalá, 28801 Alcalá de Henares, Spain;
| | - José Carlos Nieto-Borge
- Department of Physics and Mathematics, University of Alcalá, 28801 Alcalá de Henares, Spain;
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Shoji Y, Tamaki R, Okada Y. Temperature Dependence of Carrier Extraction Processes in GaSb/AlGaAs Quantum Nanostructure Intermediate-Band Solar Cells. NANOMATERIALS 2021; 11:nano11020344. [PMID: 33573008 PMCID: PMC7911294 DOI: 10.3390/nano11020344] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 01/19/2021] [Accepted: 01/25/2021] [Indexed: 11/24/2022]
Abstract
From the viewpoint of band engineering, the use of GaSb quantum nanostructures is expected to lead to highly efficient intermediate-band solar cells (IBSCs). In IBSCs, current generation via two-step optical excitations through the intermediate band is the key to the operating principle. This mechanism requires the formation of a strong quantum confinement structure. Therefore, we focused on the material system with GaSb quantum nanostructures embedded in AlGaAs layers. However, studies involving crystal growth of GaSb quantum nanostructures on AlGaAs layers have rarely been reported. In our work, we fabricated GaSb quantum dots (QDs) and quantum rings (QRs) on AlGaAs layers via molecular-beam epitaxy. Using the Stranski–Krastanov growth mode, we demonstrated that lens-shaped GaSb QDs can be fabricated on AlGaAs layers. In addition, atomic force microscopy measurements revealed that GaSb QDs could be changed to QRs under irradiation with an As molecular beam even when they were deposited onto AlGaAs layers. We also investigated the suitability of GaSb/AlGaAs QDSCs and QRSCs for use in IBSCs by evaluating the temperature characteristics of their external quantum efficiency. For the GaSb/AlGaAs material system, the QDSC was found to have slightly better two-step optical excitation temperature characteristics than the QRSC.
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Affiliation(s)
- Yasushi Shoji
- Global Zero Emission Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan; (R.T.); (Y.O.)
- Correspondence: ; Tel.: +81-29-861-8251
| | - Ryo Tamaki
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan; (R.T.); (Y.O.)
| | - Yoshitaka Okada
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan; (R.T.); (Y.O.)
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Infrared photodetector sensitized by InAs quantum dots embedded near an Al 0.3Ga 0.7As/GaAs heterointerface. Sci Rep 2020; 10:11628. [PMID: 32669650 PMCID: PMC7363919 DOI: 10.1038/s41598-020-68461-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 06/24/2020] [Indexed: 11/24/2022] Open
Abstract
Mid-infrared sensors detect infrared radiation emitted from objects, and are actually widely used for monitoring gases and moisture as well as for imaging objects at or above room temperature. Infrared photodetectors offer fast detection, but many devices cannot provide high responsivity at room temperature. Here we demonstrate infrared sensing with high responsivity at room temperature. The central part of our device is an Al0.3Ga0.7As/GaAs heterostructure containing InAs quantum-dot (QD) layer with a 10-nm-thick GaAs spacer. In this device, the electrons that have been accumulated at the heterointerface are transferred to the conduction band of the Al0.3Ga0.7As barrier by absorbing infrared photons and the following drift due to the electric field at the interface. These intraband transitions at the heterointerface are sensitized by the QDs, suggesting that the presence of the QDs increases the strength of the intraband transition near the heterointerface. The room-temperature responsivity spectrum exhibits several peaks in the mid-infrared wavelength region, corresponding to transitions from the InAs QD and wetting layer states as well as the transition from the quantized state of the triangular potential well at the two-dimensional heterointerface. We find that the responsivity is almost independent of the temperature and the maximum value at 295 K is 0.8 A/W at ~ 6.6 µm for a bias of 1 V, where the specific detectivity is \documentclass[12pt]{minimal}
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\begin{document}$$1.8\times {10}^{10}$$\end{document}1.8×1010 cmHz1/2/W.
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Sugathan A, Bhattacharyya B, Kishore VVR, Kumar A, Rajasekar GP, Sarma DD, Pandey A. Why Does CuFeS 2 Resemble Gold? J Phys Chem Lett 2018; 9:696-701. [PMID: 29343063 DOI: 10.1021/acs.jpclett.7b03190] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
While several potential applications of CuFeS2 quantum dots have already been reported, doubts regarding their optical and physical properties persist. In particular, it is unclear if the quantum dot material is metallic, a degenerately doped semiconductor, or else an intrinsic semiconductor material. Here we examine the physical properties of CuFeS2 quantum dots in order to address this issue. Specifically, we study the bump that is observed in the optical spectra of these quantum dots at ∼500 nm. Using a combination of structural and optical characterization methods, ultrafast spectroscopy, as well as electronic structure calculations, we ascertain that the unusual purple color of CuFeS2 quantum dots as well the golden luster of CuFeS2 films arise from the existence of a plasmon resonance in these materials. While the presence of free carriers causes this material to resemble gold, surface treatments are also described to suppress the plasmon resonance altogether.
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Affiliation(s)
- Anumol Sugathan
- Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560012, India
| | - Biswajit Bhattacharyya
- Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560012, India
| | - V V R Kishore
- Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560012, India
| | - Abhinav Kumar
- Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560012, India
| | - Guru Pratheep Rajasekar
- Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560012, India
| | - D D Sarma
- Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560012, India
| | - Anshu Pandey
- Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560012, India
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Prado SJ, Marques GE, Alcalde AM. Photovoltaic efficiency of intermediate band solar cells based on CdTe/CdMnTe coupled quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:445301. [PMID: 28799524 DOI: 10.1088/1361-648x/aa85c7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this work we show the calculation of optimized efficiencies of intermediate band solar cells (IBSCs) based on Mn-doped II-VI CdTe/CdMnTe coupled quantum dot (QD) structures. We focus our attention on the combined effects of geometrical and Mn-doping parameters on optical properties and solar cell efficiency. In the framework of [Formula: see text] theory, we accomplish detailed calculations of electronic structure, transition energies, optical selection rules and their corresponding intra- and interband oscillator strengths. With these results and by following the intermediate band model, we have developed a strategy which allows us to find optimal photovoltaic efficiency values. We also show that the effects of band admixture which can lead to degradation of optical transitions and reduction of efficiency can be partly minimized by a careful selection of the structural parameters and Mn-concentration. Thus, the improvement of band engineering is mandatory for any practical implementation of QD systems as IBSC hardware. Finally, our calculations show that it is possible to reach significant efficiency, up to ∼26%, by selecting a restricted space of parameters such as quantum dot size and shape and Mn-concentration effects, to improve the modulation of optical absorption in the structures.
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Affiliation(s)
- Silvio J Prado
- Faculdade de Ciências Integradas do Pontal, Universidade Federal de Uberlândia, 38.304-402, Ituiutaba-MG, Brazil
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Optimizing the Structure of Distribution Smart Grids with Renewable Generation against Abnormal Conditions: A Complex Networks Approach with Evolutionary Algorithms. ENERGIES 2017. [DOI: 10.3390/en10081097] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Wen L, Gao F, Zhang S, Li G. Growth of InAs Quantum Dots on GaAs (511)A Substrates: The Competition between Thermal Dynamics and Kinetics. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:4277-4285. [PMID: 27348495 DOI: 10.1002/smll.201503387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 05/25/2016] [Indexed: 06/06/2023]
Abstract
The growth process of InAs quantum dots grown on GaAs (511)A substrates has been studied by atomic force microscopy. According to the atomic force microscopy studies for quantum dots grown with varying InAs coverage, a noncoherent nucleation of quantum dots is observed. Moreover, due to the long migration length of In atoms, the Ostwald ripening process is aggravated, resulting in the bad uniformity of InAs quantum dots on GaAs (511)A. In order to improve the uniformity of nucleation, the growth rate is increased. By studying the effects of increased growth rates on the growth of InAs quantum dots, it is found that the uniformity of InAs quantum dots is greatly improved as the growth rates increase to 0.14 ML s(-1) . However, as the growth rates increase further, the uniformity of InAs quantum dots becomes dual-mode, which can be attributed to the competition between Ostwald ripening and strain relaxation processes. The results in this work provide insights regarding the competition between thermal dynamical barriers and the growth kinetics in the growth of InAs quantum dots, and give guidance to improve the size uniformity of InAs quantum dots on (N11)A substrates.
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Affiliation(s)
- Lei Wen
- State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510641, P. R. China
- Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province, South China University of Technology, Guangzhou, 510641, P. R. China
- Department of Electronic Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Fangliang Gao
- State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510641, P. R. China
- Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province, South China University of Technology, Guangzhou, 510641, P. R. China
- Department of Electronic Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Shuguang Zhang
- State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510641, P. R. China
- Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province, South China University of Technology, Guangzhou, 510641, P. R. China
- Department of Electronic Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Guoqiang Li
- State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510641, P. R. China
- Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province, South China University of Technology, Guangzhou, 510641, P. R. China
- Department of Electronic Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
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