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Effect of annealing temperature of MoO3 layer in MoO3/Au/MoO3 (MAM) coated PbS QDs sensitized ZnO nanorods/FTO glass solar cell
摘要： This research reports fabrication of MoO3/Au/MoO3 (MAM) coated PbS sensitized quantum dot solar cell. ZnO nanorod grown FTO glass substrates were sensitized by PbS quantum dots (PbS QDs/ZnO nanorods/FTO Glass), followed by (MoO3/Au/MoO3) coating. Hydrothermal process was used to grow ZnO nanorods, followed by the deposition of PbS QDs using Successive Ionic Layer Adsorption and Reaction (SILAR). Finally, (MoO3/Au/MoO3) layers were deposited for the back contact. Spin coating was used to deposit MoO3 layers while middle layer of Au was deposited by sputter coating. Three such devices were fabricated with three di?erent annealing temperatures i.e. 100 °C, 150 °C and 200 °C for ?rst MoO3 layer. Scanning Electron Microscopy (SEM) was used for surface morphology of the devices; Energy Dispersive Spectroscopy Analysis (EDS) and X-Ray Di?raction (XRD) techniques were used for elemental and structural analysis, Optical properties of the devices were determined using UV–Visible analysis. Power conversion e?ciency (PCE) of all three devices was obtained to observe devices performance. Improved PCE of 4.617% was obtained by the device with the thermal treatment of 150 °C.
关键词： Quantum dots,ZnO nanorods,MoO3 thin ?lm,PbS quantum dot sensitized Solar Cell
更新于2025-09-23 15:19:57
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Anomalous Fano Resonance in Double Quantum Dot System Coupled to Superconductor
摘要： We analyze the influence of a local pairing on the quantum interference in nanoscopic systems. As a model system we choose the double quantum dot coupled to one metallic and one superconducting electrode in the T-shape geometry. The analysis is particularly valuable for systems containing coupled objects with considerably different broadening of energy levels. In such systems, the scattering of itinerant electrons on a discrete (or narrow) energy level gives rise to the Fano-type interference. Systems with induced superconducting order, along well understood fano resonances, exhibit also another features on the opposite side of the Fermi level. The lineshape of these resonances differs significantly from their reflection on the opposite side of the Fermi level, and their origin was not fully understood. Here, considering the spin-polarized tunneling model, we explain a microscopic mechanism of a formation of these resonances and discuss the nature of their uncommon lineshapes. We show that the anomalous Fano profiles originate solely from the pairing of nonscattered electrons with scattered ones. We investigate also the interplay of each type of resonances with the Kondo physics and discuss the resonant features in differential conductivity.
关键词： Kondo physics,Fano-type interference,quantum interference,spin-polarized tunneling model,differential conductivity,double quantum dot,superconducting electrode,nanoscopic systems
更新于2025-09-23 15:19:57
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Effect of co-sensitization of InSb quantum dots on enhancing the photoconversion efficiency of CdS based quantum dot sensitized solar cells
摘要： The effect of co-sensitization of CdS and InSb Quantum Dots (QDs) on the enhancement of efficiency of Quantum Dots Sensitized Solar Cells (QDSSCs) has been investigated. InSb is synthesized by a facile solvothermal method using indium metal particles and antimony trichloride as precursors. From TEM images the average particle size of InSb was found to be less than 25 nm. The I–V data showed photoconversion efficiency (PCE) of 0.8% using InSb QDs as a sensitizer layer for QDSSC. However, co-sensitization of InSb QDs and CdS QDs on the TiO2 photoanode in QDSSCs showed an enhanced PCE of 4.94% compared to that of CdS sensitized solar cells (3.52%). The InSb QD layer broadens the light absorption range with reduced spectral overlap causing an improvement in light harvesting along with suppression of surface defects which reduced the recombination losses. As a result, co-sensitized TiO2/CdS/InSb QDSSC exhibits a greatly improved PCE of 4.94%, which is 40% higher than that of TiO2/CdS (3.52%) based QDSSCs due to improved light absorption with low recombination losses.
关键词： quantum dot sensitized solar cells,co-sensitization,photoconversion efficiency,CdS,InSb quantum dots
更新于2025-09-23 15:19:57
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Light extraction from quantum dot light emitting diodes by multiscale nanostructures
摘要： Improving the light extraction efficiency by introducing optical–functional structures outside of quantum dot light emitting diodes (QLED) for further enhancing the external quantum efficiency (EQE) is essential for its application in display and lighting industrialization. Although the efficiency of QLED has been optimized by controlling of the synthesis of the quantum dots, the low outcoupling efficiency is indeed unresolved because of total internal reflections, waveguides and metal surface absorptions within the device. Here, we are utilizing multiscale nanostructures attaching to the outer surface of the glass substrate to extract the trapped light from the emitting layers of QLED. The result indicates that both the EQE and luminance are improved from 12.29% to 17.94% and 122400 cd m-2 to 178700 cd m-2, respectively. The maximum EQE and current efficiency improve to 21.3% and 88.3 cd A?1, respectively, which are the best performance among reported green QLED with light outcoupling nanostructures. The improved performance is ascribed to eliminate total internal reflection by multiscale nanostructures attached to the outer surface of the QLED. Additionally, the simulation result of Finite-difference time domain (FDTD) also demonstrates the light trapping effect is reduced by the multiscale nanostructures. The design of the novel light outcoupling nanostructure for further improving the efficiency of QLED can promote its application in display and lighting industrializations.
关键词： quantum dot light emitting diodes,multiscale nanostructures,light extraction efficiency,external quantum efficiency,display and lighting industrialization
更新于2025-09-23 15:19:57
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Electro-absorption and Electro-optic Characterization of L-Band InAs/InP Quantum-dash Waveguide
摘要： Electro-absorption and electro-optic characteristics of InAs/InP quantum-dash active region-based waveguide, emitting at ~1600 nm is investigated. Two major peaks were observed in the change of absorption spectrum with a maximum value of 7070 cm-1 at a bias voltage of -8V with an excellent uniform extinction ratio of ~15 dB across the wavelength range of operation (1460-1620 nm). The effect of temperature on electro-absorption (EA) measurement suggest a strong influence resulting in merging of two major change of absorption spectrum peaks with higher temperature. Furthermore, electro-optic measurements indicate a change in refractive index and its efficiency values of ~2.9×10-4 and ~0.5×10-4 V-1, respectively, hence exhibiting a low chirping factor of 0.9 and 1.5 at bias voltages of -2 V and -4 V, respectively. As a quasi-three-dimensionally confined structure possessing both quantum well- and quantum dot-like features, the quantum dash waveguide showed superior electro-absorption and electro-optic properties compared to quantum dots and close to that of quantum wells, while attaining low chirp and broad wavelength range of operation. This paves a way for potential realization of quantum dash-based EA and electro-optic modulator for future optical access networks, particularly operating in wide C- to L-band region.
关键词： quantum-dot,modulators,electro-optic,electro-absorption,Quantum-dash
更新于2025-09-23 15:19:57
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Efficient Structure for InP/ZnS-Based Electroluminescence Device by Embedding the Emitters in the Electron-Dominating Interface
摘要： The charge-carrier distribution has been an important parameter in determining the efficiency of quantum-dot-based light-emitting diodes (QLEDs). In this Letter, we demonstrate a new inverted device structure of ITO/ZnO/polyethylenimine/quantum dots (QDs)/1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi)/4,4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP)/MoO3/Al for improving the efficiency of InP-QD-based QLEDs. By introducing a thin layer of electron transport materials, the hole accumulation at the hole transport layer and the QD interface is largely reduced, which suppresses the quenching effect of holes on the QD emission. Compared with the conventional device structure with the emitters at ZnO/CBP pn junction, the peak current efficiency (external quantum efficiency) increases from 3.83 (5.17 cd/A) to 6.32% (8.54 cd/A) by imbedding the QDs at the electron-dominating interface of ZnO/TPBi. The analysis reveals that an internal quantum efficiency of nearly 100% is achieved for the InP-QD-based device (with a photoluminescence quantum yield of 32%). This work provides an alternative device structure for achieving high-efficiency QLED devices.
关键词： electron transport materials,quantum-dot-based light-emitting diodes,internal quantum efficiency,charge-carrier distribution,InP-QD-based QLEDs
更新于2025-09-23 15:19:57
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Optical and electronic properties of CdTe quantum dots in their freezed solid matrix phase and solution phase
摘要： The present work deals with the comparison of sizes, optical and electronic properties of COOH functionalized CdTe quantum dots (QDs) in freezed solid polymeric (polyvinyl alcohol (PVA) matrix and in solution phase (water). PVA has been chosen as host material for guest CdTe QDs because of its unique properties like hydrophilicity, good thermo stability, and easy process ability. Experimental absorption, emission, X-Ray diffraction spectra and electronic band gap have been studied by UV–Vis absorption, luminescence and X-Ray diffraction spectroscopy. The smaller size of CdTe QDs in solid PVA polymer matrix ((cid:1)6 nm) and larger band gap of (cid:1)9.5 eV validates their quantum con?nement regime in freezed solid phase. The smaller particle size in solid phase compared to that of the particle size in its solution phase (8 nm) validates the non existence of agglomeration in solid phase. Appearance of high intense and wide luminescence emission in solid form proves the strong candidature of CdTe QDs as promising sensors for today’s optoelectronic and biomedical industry.
关键词： Quantum Dot,CdTe/PVA thin ?lm,Quantum con?nement,UV–Visible,Photoluminsence spectroscopy
更新于2025-09-23 15:19:57
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Coupled electronic states in CdTe quantum dot assemblies fabricated by utilizing chemical bonding between ligands
摘要： Semiconductor quantum dot superlattices (QDSLs) have attracted much attention as key materials for realizing new optoelectronic devices such as solar cells with high conversion efficiency and thermoelectric elements with high electrical conductivity. To improve the charge transport properties in the QDSL-based optoelectronic devices, it is important for the QD structures to form minibands, which are the coupled electronic states between QDs. A shorter inter-QD distance and a periodic arrangement of QDs are the essential conditions for the formation of minibands. In this study, we use CdTe QDs capped with short ligands of N-acetyl-L cysteine (NAC) to fabricate a three-dimensional QD assemblies by utilizing the chemical bonding between NACs. The absorption spectra clearly display the quantum resonance phenomenon originating from the coupling of the wave functions between the adjacent QDs in the CdTe QD assemblies. Furthermore, we demonstrate the formation of minibands in the CdTe QD assemblies by examining both, the excitation energy dependence of the photoluminescence (PL) spectra and the detection energy dependence of the PL excitation spectra. The fabrication method of QD assemblies utilizing the chemical bonding between NACs can be applied to all QDs capped with NAC as a ligand.
关键词： Quantum resonance,Quantum dot,Superlattice,Miniband
更新于2025-09-23 15:19:57
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Theoretical investigation of the transient regime of electromagnetically induced transparency in spherical quantum dot with on-center hydrogen impurity
摘要： The transient evolution of the susceptibility of the spherical quantum dot with an on-center hydrogen impurity, interacting with the continuous wave lasers, with respect to the probe field is studied numerically and analytically by solving optical Bloch equations. The influence of the control Rabi frequency, dephasing rates and laser detunings is discussed. The damped oscillatory behaviour is observed, as well as the amplification of the probe laser light before the stationary regime of the electromagnetically induced transparency is achieved.
关键词： Quantum dot,Hydrogenic impurity,Electromagnetically induced transparency,Transient regime
更新于2025-09-23 15:19:57
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Simultaneous effects of pressure, temperature, impurity location, SOI and magnetic field on THG of a pyramid quantum dot
摘要： We have investigated simultaneous effects of pressure, temperature, impurity location, Rashba and Dresselhaus spin–orbit interaction and magnetic field on THG of realized GaAs/Al0.5Ga0.5As pyramid quantum dot with considering the wet layer. For this purpose, we have calculated the energy levels and wave function of one electron that is confined in constant potential, in presence of impurity, magnetic field, Rashba and Dresselhous SOI in various temperatures, pressure and impurity location in effective mass approximation by FEM. In the following, we have presented the effect of magnetic field, Rashba and Dresselhous SOI, temperature, pressure and impurity location on THG in various conditions. Results show that: (1) THG increases by increasing the magnetic field and the distance between the peaks decrease. Also, the peak corresponding to the E21 transition has a blue shift and the peaks corresponding to the E31/2 and E41/3 transitions have a red shift. (2) THG decreases and shifts to higher energies and has a small blue shift by augment of temperature. (3) THG enhances and all of peaks have a red shift by increment of pressure. (4) THG has a minimum around z0 = 4 nm in all magnetic field, temperature and pressure cases. Also, all of peaks have a blue shift by augment of z0 until z0 = 4 nm and then have a red shit by increasing the z0.
关键词： Pyramid quantum dot,Spin orbit interaction,Third harmonic generation
更新于2025-09-23 15:19:57