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Molecular States of Composite Fermions in Self-Organized InP/GaInP Quantum Dots in Zero Magnetic Field
摘要： The size and positions of regions of line localization and the magnetic-field (0–10 T) dependence of the low-temperature (10 K) photoluminescence spectra of single InP/GaInP quantum dots with a number of electrons of N = 5–7 and a Wigner–Seitz radius of ~2.5 are determined using a near-field scanning optical microscope. The formation of composite fermion molecules with a size coinciding with that of localization regions and bond lengths of ~30 and 50 nm, respectively, at a Landau-level filling factor from 1/2 to 2/7 in zero magnetic field is established. At N = 6, the pairing and rearrangement of composite fermions under photoexcitation are found, which offers opportunities for the use of InP/GaInP quantum dots to create a magnetic-field-free topological quantum gate.
关键词： InP/GaInP quantum dots,near-field scanning microscopy,photoluminescence,composite fermions,topological quantum gate
更新于2025-09-23 15:19:57
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Investigation of polycrystalline Ga <sub/>x</sub> In <sub/>1a??a??a??x</sub> P for potential use as a solar cell absorber with tunable bandgap
摘要： There is ongoing interest in developing a stable, low-cost, 1.6–1.8 eV top-cell material that can be used for two-junction (tandem) solar cells, particularly in combination with a silicon bottom cell. In this work, polycrystalline GaInP is grown and characterized to explore its properties and use for this purpose. The film composition and deposition temperature are varied to determine their effects on grain size, morphology, and photoluminescence (PL) over a range of bandgaps from 1.35 to 1.7 eV. An Al-assisted post-deposition treatment for 1.7-eV polycrystalline GaInP results in a 90-fold increase in peak photoluminescence (PL) intensity, a 220-fold increase in integrated PL intensity, and increased time-resolved PL lifetime from <2 ns to 44 ns. The increase in PL intensity and lifetime is attributed to a reduction of nonradiative minority-carrier recombination at the top surface, and at grain boundaries near the surface, due to the formation of a higher-bandgap AlGaInP alloy. These materials provide a viable path toward increased minority-carrier concentration under illumination and improved recombination properties needed for high-efficiency tandem solar cells.
关键词： polycrystalline GaInP,tunable bandgap,post-deposition treatment,photoluminescence,solar cell
更新于2025-09-23 15:19:57
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Improving Radiation Resistance of GaInP/GaInAs/Ge Triple-Junction Solar Cells Using GaInP Back-Surface Field in the Middle Subcell
摘要： This paper studies the radiation resistance for GaInP/GaInAs/Ge triple-junction space solar cells with a GaInP back-surface ?eld (BSF) in the GaInAs middle subcell compared with those with an AlGaAs BSF. The results show that the initial electrical performance is almost the same for both of them. However, the radiation resistance of the GaInP BSF cell was improved. After irradiation by 1 MeV electron beam with a cumulative dose of 1015 e/cm2, the Jsc declined by 4.73% and 6.61% for the GaInP BSF cell and the AlGaAs BSF cell, respectively; the e?ciency degradation was 13.64% and 14.61% for the GaInP BSF cell and the AlGaAs BSF cell, respectively, leading to a reduced degradation level of 6%. The mechanism for GaInP BSF to improve the radiation resistance of GaInP/GaInAs/Ge triple-junction solar cells is also discussed in this work. Similar results were obtained when irradiation cumulative doses varied from 1 × 1014 e/cm2 to 1 × 1016 e/cm2.
关键词： back-surface ?eld,electron beam irradiation,GaInP/GaInAs/Ge triple-junction space solar cell,radiation resistance
更新于2025-09-23 15:19:57
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Minimal Magnetic Dipole Moment for the Solar Cell Array Using GaInP/GaAs/Ge Cells
摘要： The only ambient power source in space is solar energy, which is harvested by photovoltaic conversion with solar cells. Since about 20 years ago, silicon solar cells have been used extensively as the primary power devices in space. However, in recent years, GaInP/GaAs/Ge solar cells with triple junction technology, have been widely used as power-generation devices for space applications. Not only do the GaInP/GaAs/Ge solar cells have better conversion efficiency compared to Si solar cells, but it is also possible to supply the required electric power using a smaller number of solar cells. While there are advantages when using the GaInP/GaAs/Ge solar cells, methods for design of systems of strings should be established for minimizing their magnetic dipole moment. This is because the voltage and current are three times greater than with Si solar cells, and this must be considered. By electromagnetic theory, loop current of a string consisting of cells in series occurs when flowing through it. That magnetic dipole moment can affect attitude control when using magnetic torque bars in orbit, and spacecraft systems require no more than 0.25 Am2 of magnetic dipole moment for optimal attitude control. Therefore, we designed a single string of GaInP/GaAs/Ge solar cells and tested its current capacity to see and minimize the magnetic dipole moment. Finally, we proposed an optimal string design methodology by a test coupon solar cell array using GaInP/GaAs/Ge solar cells by simulation and implemented it on a substrate of carbon fiber reinforced plastic material to see how well the prototype worked or did not work. In future, the string design methodology could be extended to a larger solar cell array by using this coupon design methodology to minimize the magnetic dipole moment.
关键词： Carbon fiber reinforced plastics,GaInP/GaAs/Ge,Solar cell,String,Magnetic dipole moment
更新于2025-09-19 17:13:59
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quantum dots: Insights from time-dependent density functional theory
摘要： Colloidal quantum dots (QDs) of group III-V are considered as promising candidates for next-generation environmentally friendly light emitting devices, yet there appears to be only limited understanding of the underlying electronic and excitonic properties. Using large-scale density functional theory with the hybrid B3LYP functional solving the single-particle states and time-dependent density functional theory accounting for the many-body excitonic effects, we have identified the structural, electronic, and excitonic optical properties of InP, GaP, and GaInP QDs containing up to a thousand atoms or more. The calculated optical gap of InP QD appears in excellent agreement with available experiments, and it scales nearly linearly with the inverse diameter. The radiative exciton decay lifetime is found to increase surprisingly linearly with increasing the dot size. For GaP QDs we predict an unusual electronic state crossover at a diameter of around 1.5 nm, whereby the nature of the lowest unoccupied molecular orbital (LUMO) state switches its symmetry from (cid:2)5-like at a larger diameter to (cid:2)1-like at a smaller diameter. After the crossover, the absorption intensity of the band-edge exciton states is significantly enhanced. Finally, we find that Vegard’s law holds very well for GaInP random alloyed quantum dots down to ultrasmall sizes with less than a hundred atoms. The obtained energy gap bowing parameter of this common-cation compound in QD regime appears positive, size-dependent, and much smaller than its bulk parentage. The volume deformation, dominating over the charge exchange and structure relaxation effects, is mainly responsible for the QD energy gap bowing. The impact of excitonic effects on the optical bowing is found to be marginal. The present work provides a road map for a variety of electronic and optical properties of colloidal QDs in group III-V that can guide spectroscopic studies.
关键词： InP,excitonic properties,time-dependent density functional theory,GaInP,quantum dots,GaP
更新于2025-09-11 14:15:04
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Temperature-dependent photoluminescence processes of GaInP top cell irradiated with 11.5?MeV and 1.0?MeV electrons
摘要： The effects of 11.5 MeV electrons irradiation on the GaInP top cell of GaInP/GaAs/Ge triple-junction solar cells have been investigated by temperature-dependent photoluminescence (PL) measurements. The thermal quenching of PL intensity is observed in the temperature range of 10 K–270 K, attributing to the nonradiative recombination centers H2 (Ev + 0.55 eV) hole trap and H3 (Ev + 0.76 eV) hole trap. A slight negative thermal quenching (NTQ) of PL intensity exists at nearly 300 K and could be associated with the 0.18 eV intermediate states. The temperature-dependent photoluminescence process of GaInP top cell irradiated with 11.5 MeV electrons differs with that irradiated with 1.0 MeV electrons.
关键词： Photoluminescence,Electron irradiation,GaInP top cell,Negative thermal quenching
更新于2025-09-04 15:30:14