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Ruiz N, Fernández D, Stanojević L, Ben T, Flores S, Braza V, Carro AG, Luna E, Ulloa JM, González D. Suppressing the Effect of the Wetting Layer through AlAs Capping in InAs/GaAs QD Structures for Solar Cells Applications. NANOMATERIALS 2022; 12:nano12081368. [PMID: 35458076 PMCID: PMC9030006 DOI: 10.3390/nano12081368] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 04/07/2022] [Accepted: 04/11/2022] [Indexed: 01/27/2023]
Abstract
Recently, thin AlAs capping layers (CLs) on InAs quantum dot solar cells (QDSCs) have been shown to yield better photovoltaic efficiency compared to traditional QDSCs. Although it has been proposed that this improvement is due to the suppression of the capture of photogenerated carriers through the wetting layer (WL) states by a de-wetting process, the mechanisms that operate during this process are not clear. In this work, a structural analysis of the WL characteristics in the AlAs/InAs QD system with different CL-thickness has been made by scanning transmission electron microscopy techniques. First, an exponential decline of the amount of InAs in the WL with the CL thickness increase has been found, far from a complete elimination of the WL. Instead, this reduction is linked to a higher shield effect against QD decomposition. Second, there is no compositional separation between the WL and CL, but rather single layer with a variable content of InAlGaAs. Both effects, the high intermixing and WL reduction cause a drastic change in electronic levels, with the CL making up of 1–2 monolayers being the most effective configuration to reduce the radiative-recombination and minimize the potential barriers for carrier transport.
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Affiliation(s)
- Nazaret Ruiz
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
- Correspondence: (N.R.); (D.F.)
| | - Daniel Fernández
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
- Correspondence: (N.R.); (D.F.)
| | - Lazar Stanojević
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Avda. Complutense 30, 28040 Madrid, Spain; (L.S.); (A.G.C.); (J.M.U.)
| | - Teresa Ben
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
| | - Sara Flores
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
| | - Verónica Braza
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
| | - Alejandro Gallego Carro
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Avda. Complutense 30, 28040 Madrid, Spain; (L.S.); (A.G.C.); (J.M.U.)
| | - Esperanza Luna
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, D-10117 Berlin, Germany;
| | - José María Ulloa
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Avda. Complutense 30, 28040 Madrid, Spain; (L.S.); (A.G.C.); (J.M.U.)
| | - David González
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
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Xu Y, Wang W, Chen Z, Sui X, Wang A, Liang C, Chang J, Ma Y, Song L, Jiang W, Zhou J, Liu X, Zhang Y. A general strategy for semiconductor quantum dot production. NANOSCALE 2021; 13:8004-8011. [PMID: 33956919 DOI: 10.1039/d0nr09067k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Mass production of semiconductor quantum dots (QDs) from bulk materials is highly desired but far from being satisfactory. Herein, we report a general strategy to mechanically tailor semiconductor bulk materials into QDs. Semiconductor bulk materials are routinely available via simple chemical precipitation. From their bulk materials, a variety of semiconductor (e.g., lead sulfide (PbS), cadmium sulfide (CdS), copper sulfide (CuS), ferrous sulfide (FeS), and zinc sulfide (ZnS)) QDs are successfully produced in high yields (>15 wt%). This is achieved by a combination of silica-assisted ball-milling and sonication-assisted solvent treatment. The as-produced QDs show intrinsic characteristics and outstanding water solubility (up to 5 mg mL-1), facilitating their practical applications. The QD dispersions present remarkable photoluminescence (PL) with exciton-dependence and nanosecond (ns)-scale lifetimes. The QDs-poly(methyl methacrylate) (PMMA) hybrid thin films demonstrate exciting solid-state fluorescence and exceptional nonlinear saturation absorption (NSA). Absolute modulation depths of up to 58% and saturation intensities down to 0.40 MW cm-2 were obtained. Our strategy could be applied to any semiconductor bulk materials and therefore paves the way for the construction of the complete library of semiconductor QDs.
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Affiliation(s)
- Yuanqing Xu
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
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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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