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: From quantum dots to bulk crystals and additional boundary conditions for Rydberg exciton-polaritons
摘要： We propose schemes for calculation of optical functions of a semiconductor with Rydberg excitons for a wide interval of dimensions. We have started with a zero-dimensional structure (quantum dot), then going to one-dimensional (quantum wire), two-dimensional (quantum wells and wide quantum wells), and ?nally three-dimensional bulk crystals; our analytical ?ndings are illustrated numerically, showing an agreement with available experimental data. Calculations including exciton-polaritons are performed; the case of a large number of polariton branches is discussed, and obtained theoretical absorption spectra show good agreement with experimental data.
关键词： quantum wells,bulk crystals,exciton-polaritons,quantum wires,Rydberg excitons,quantum dots
更新于2025-09-23 15:21:01
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Visible-Light Driven Photocatalytic Hydrogen Generation by Water-Soluble All-Inorganic Core-Shell Silicon Quantum Dots
摘要： The photocatalytic hydrogen (H2) generation by boron (B) and phosphorus (P) codoped silicon quantum dots (Si QDs) with diameters in the quantum confinement regime is investigated. The codoped Si QDs have an amorphous shell made from B, Si and P. The shell induces negative potential on the surface and makes codoped Si QDs dispersible in water. The hydrophilic shell offers enhanced stability and efficiency in the photocatalytic H2 generation and provides the opportunity to study the size dependence of the H2 generation rate. A drastic increase of the H2 generation rate with decreasing the QD size is observed. Analyses based on the Marcus theory reveal that the upper shift of the lowest unoccupied molecular orbital level of Si QDs by the quantum confinement effect is responsible for the enhanced photocatalytic activity.
关键词： silicon quantum dots,quantum confinement,Marcus theory,photocatalytic hydrogen generation
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE CHILEAN Conference on Electrical, Electronics Engineering, Information and Communication Technologies (CHILECON) - Valparaiso, Chile (2019.11.13-2019.11.27)] 2019 IEEE CHILEAN Conference on Electrical, Electronics Engineering, Information and Communication Technologies (CHILECON) - Fourier-Bessel Shapes in Output Photocurrents and Frequency Chirping Effects from Laser Fields
摘要： Record low values in this material system of threshold current density, particularly at elevated temperature, are presented for InP quantum dot lasers. Lasers with Ga0 .5 8 In0 .4 2 P in the dot upper con?ning layer have the lowest threshold current densities, 138 A·cm?2 at 300 K, and 235 A·cm?2 at 350 K (77 °C) (2-mm lasers, uncoated facets). Gain-current density data suggests laser performance with an upper con?ning layer of Gax In1 ?xP with x = 0.54, 0.56 or 0.58 would be similar if not for the very low internal optical mode loss, αi of samples with x = 0.56 and 0.58. Gain measurements at ?xed inversion level suggest that increasing x content in Gax In1 ?xP increases gain at ?xed inversion level but samples with x = 0.54 also exhibit reduced recombination current density. The increasing recombination current density at elevated temperature due to thermal carrier spreading is signi?cantly reduced in samples with x = 0.56 and x = 0.58 but measurements at common operating points attribute this largely to the reduced αi for these samples and given the same αI , samples with x = 0.54, 0.56 and 0.58 would all bene?t from reduced effects due to thermal carrier spreading compared to x = 0.52.
关键词： Quantum dot devices,InP self-assembled quantum dots,semiconductor laser,short wavelength lasers,threshold current density,temperature sensitivity
更新于2025-09-23 15:21:01
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Electrochemiluminescence revealing that HNO3-oxidized single-walled carbon nanotubes are essentially tubular graphene quantum dot-nanoassemblies
摘要： Graphene quantum dots (GQDs) as recently emerging 0-D graphitic nanomaterials, have attracted much attention due to their unique optical, electrical and catalytic properties. However, some properties of GQDs, such as very small size, low density, and excellent water-solubility, make it difficult to be separated and immobilized. This may limit the recycle and purification of GQDs, and thus their applications in catalysis and sensing. In this work, we prepared tubular GQD-nanoassemblies (t-GQD-NAs) by etching single-walled carbon nanotubes (SWCNTs) with concentrated HNO3. The synthesized t-GQD-NAs were characterized by TEM, SEM, XPS, Raman spectroscopy and electrochemiluminescence (ECL) in details. t-GQD-NAs were much shorter and slimmer in morphology, bore more oxygen-containing groups, and had a higher surface defect density compared with SWCNTs. t-GQD-NAs not only maintained good UV absorption property of SWCNTs but also showed strong infrared ECL emission and broad ECL spectrum, verifying that t-GQD-NAs were assembled from GQDs of various sizes and some graphene nanoribbons. This is for the first time that 0-D GQDs were reported to be assembled into 1-D tubular carbon structures. The t-GQD-NAs with abundant surface states and good ECL activity could be easily separated, purified, and immobilized, suggesting their promising applications in ECL sensing and catalysis.
关键词： Graphene quantum dots,Single-walled carbon nanotubes,Electrochemiluminescence,Tubular graphene quantum dot-nanoassemblies
更新于2025-09-23 15:21:01
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Highly green fluorescent Nb2C MXene quantum dots
摘要： Here two dimensional Nb2C quantum dots with green fluorescence were fabricated for the first time with quantum yield (QY) up to 19%, the highest reported Nb2C dots so far with good photostability and pH stability. The S,N doping on Nb2C were considered as the main reason to enhance the high QY of Nb2C dots and was proved by the density functional theory (DFT) calculation. It was demonstrated that the fluorescent probe could be utilized effectively for 3D brain organoid labeling and embraces huge prospects in biological sensing.
关键词： green fluorescence,S,N doping,Nb2C quantum dots,3D brain organoid labeling,quantum yield
更新于2025-09-23 15:21:01
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Highly Efficient and Stable CsPbBr3 Perovskite Quantum Dots by Encapsulating in Dual-Shell Hollow Silica Spheres for WLEDs
摘要： Poor stability of CsPbX3 (X = Cl, Br or I) perovskite quantum dots (QDs) has greatly hindered their practical photoelectric applications, and how to improve it still remains a critical challenge. Herein, we encapsulated the CsPbBr3 QDs into a dual-shell hollow silica (SiO2) spheres via a simple successive ionic layer adsorption and reaction (SILAR) method. The hierarchical dual-shell structures permit CsPbBr3 QDs to be anchored on the interior of the SiO2 spheres while keeping the outside surface undisturbed, which can protect CsPbBr3 QDs from direct exposure to the atmosphere. Due to the comprehensive protection of dual-shell hollow SiO2 spheres, the CsPbBr3/SiO2 nanospheres exhibit markedly enhanced stability against light and heat, with residual PL intensity of 89% after continuous exposure of 72 h to UV light and 65% at 100?C heat treatment, respectively. In addition, an optimal PLQY of 89% is obtained with suppressed nonradiative recombination. Finally, the fabricated white light-emitting diodes (LEDs) device by employing CsPbBr3/SiO2 green phosphors could achieve a wide color gamut covering up to 136% of the NTSC standard. This work provides a novel SiO2-based encapsulation approach to solve the intrinsic instability issues of CsPbBr3 QDs, which has a profound impact on their practical applications.
关键词： photoluminescence quantum yield,CsPbBr3 quantum dots,dual-shell hollow silica spheres,stability,white light-emitting diodes
更新于2025-09-23 15:21:01
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Effect of indium alloying on the charge carrier dynamics of thick-shell InP/ZnSe quantum dots
摘要： Thick-shell InP/ZnSe III–V/II–VI quantum dots (QDs) were synthesized with two distinct interfaces between the InP core and ZnSe shell: alloy and core/shell. Despite sharing similar optical properties in the spectral domain, these two QD systems have differing amounts of indium incorporation in the shell as determined by high-resolution energy-dispersive x-ray spectroscopy scanning transmission electron microscopy. Ultrafast fluorescence upconversion spectroscopy was used to probe the charge carrier dynamics of these two systems and shows substantial charge carrier trapping in both systems that prevents radiative recombination and reduces the photoluminescence quantum yield. The alloy and core/shell QDs show slight differences in the extent of charge carrier localization with more extensive trapping observed in the alloy nanocrystals. Despite the ability to grow a thick shell, structural defects caused by III–V/II–VI charge carrier imbalances still need to be mitigated to further improve InP QDs.
关键词： indium alloying,InP/ZnSe,charge carrier dynamics,photoluminescence quantum yield,quantum dots
更新于2025-09-23 15:21:01
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Unprecedented charge state control in graphene quantum dots
摘要： High-quality double quantum dots in bilayer graphene are realized with controlled charge down to one electron. These devices provide a promising basis for spin-based qubits with long spin lifetimes.
关键词： Quantum dots,graphene,spintronics,quantum information
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Hot-Carrier Extraction in InAs/GaAs Quantum Dot Superlattice Solar Cells
摘要： We demonstrated hot-carrier (HC) extraction in GaAs solar cells containing InAs/GaAs quantum dot superlattices (QDSLs) functioning as a light absorber at 15 K. The short-circuit current density and the open-circuit voltage in the QDSL solar cells show step-wise changes as a function of the excitation photon density because of state filling under below-bandgap excitation. Furthermore, the short-circuit current density and the open-circuit voltage originated from the HC extraction were enhanced by increasing the period of the QDSL due to the improved absorptivity.
关键词： InAs quantum dots,GaAs,quantum dot superlattices,energy-selective barrier,hot-carrier solar cells
更新于2025-09-23 15:21:01
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Graphene for Flexible Lighting and Displays || Graphene-based quantum dot emitters for light-emitting diodes
摘要： Quantum dot is a zero-dimensional material that is introduced from the quantum con?nement effect when it is sized in nanometer scale and has various electrical and optical properties depending on the size of the particle. The electrons con?ned in small areas of nanoscale which are smaller than exciton Bohr radius are quantized and limited in free motion, and electrons in quantum dot are con?ned in every three direction by the quantum con?nement effect which causes a ?nite number of electron, hole, and exciton states, resulting in various characteristics on the size of the particle. In other words, the full con?nement in every three direction results in the complete quantization or discretization of the energy states of con?ned charge carriers in quantum dot [1]. Therefore, the fewer energy levels are quanti?ed as the energy level of the carrier decreases as the particle size decreases, resulting in a wider and more discretized bandgap [2e4].
关键词： electroluminescence,light-emitting diodes,quantum confinement,graphene quantum dots,photoluminescence
更新于2025-09-23 15:21:01