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Magnetron sputtered SnO <sub/>2</sub> constituting double electron transport layers for efficient PbS quantum dots solar cells
摘要： In this work, for the first time, we have successfully demonstrated that radiofrequency (RF) magnetron sputtered SnO2 can be a qualified alternative electron transport layer (ETL) for high-efficiency PbS quantum dot (QD) solar cell. Our highest-performing device using such a SnO2 ETL obtained an efficiency of 8.4%, which is comparable to the sol-gel ZnO based one (8.8%). The excellent performance mainly results from the improved current density, which is attributed to the superior properties of SnO2 ETL, such as the high electron mobility and excellent optical transmittance. However, we also found that the sputtered SnO2 based devices show smaller voltage and fill factor due to the unsatisfied surface morphology and energy level alignment. By combining a thin (around 10 nm) sol-gel ZnO film on top of sputtered SnO2 film to form the double ETL, we obtained the best efficiency of 10.1%, which is the highest efficiency for using SnO2 ETL in PbS QD solar cell. Our work not only provides a new avenue to improve the efficiency of PbS QD solar cells but also offers the possibility to use the industry compatible sputtering technique for PbS QD solar cells.
关键词： electron transporting layer,SnO2,magnetron sputtering,PbS,quantum dot solar cell
更新于2025-09-23 15:21:01
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Large Performance Enhancement in All-Solution-Processed, Full-Color, Inverted Quantum Dot Light-Emitting Diodes by Using Graphene Oxide-Doped Hole Injection Layer
摘要： Solution-processed hole injection layers (HILs) for full-color, inverted quantum dot light-emitting diodes (QLEDs) are developed by simply incorporating the graphene oxide (GO) into poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The excellent wettability of the GO-doped PEDOT:PSS mixture facilitates the effective deposition of HIL onto the organic underlayer. Ultraviolet photoelectron spectroscopy and Raman spectroscopy characterization reveal that the GO-doped PEDOT:PSS HIL possesses the advantages of increased work function and improved conductivity. Thus, the GO-doped PEDOT:PSS HIL can promote hole injection from the top anode into the device by reducing the hole injection barrier and sheet resistance. As a result, by using the GO-doped PEDOT:PSS HIL, we have successfully demonstrated highly bright all-solution-processed, full-color, inverted QLEDs showing remarkably enhanced luminance of 142165, 63318, and 3019 cd/m2 for green, red, and blue devices, respectively. To the best of our knowledge, the green device’s luminance is the best for all-solution-processed inverted green QLEDs. These results suggest that the GO-doped PEDOT:PSS is a promising candidate for high-quality HIL in all-solution-processed QLEDs with an inverted structure.
关键词： Optical,Quantum Dot Light-Emitting Diodes,Hole Injection Layer,Plasmonics,Magnetic,Hybrid Materials,Graphene Oxide,PEDOT:PSS
更新于2025-09-23 15:21:01
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Transition kinetics of impurity doped quantum dots under time-dependent confinement potential: role of noise
摘要： Present study endeavors to analyze the role of Gaussian white noise and fluctuating confinement potential on time-average excitation rate (TAER) of impurity doped quantum dot (QD). The TAER profiles are exhaustively monitored as a number of physical quantities are varied over a range with and without noise. Application of noise to the system takes place in two different pathways known as ‘additive’ and ‘multiplicative’. And the fluctuation of the confinement potential has been considered to be cosinusoidal and random which induces the excitation of ground state electronic population to the higher states. The TAER profiles comprise of features like steady increase/decrease, maximization, minimization and saturation. However, the specific characteristics of a particular profile depend on presence/absence of noise, the noise mode, the nature of fluctuating confinement potential and the identity of the physical quantity being varied. Production of large TAER of doped QD depends on noise-mode and nature of fluctuating confinement potential based on which the noise strength is required to be maintained in the vicinity of some typical values.
关键词： additive noise,Gaussian white noise,time-average excitation rate,impurity doped quantum dot,multiplicative noise,fluctuating confinement potential
更新于2025-09-23 15:21:01
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Transiently changing shape of the photon number distribution in a quantum-dota??cavity system driven by chirped laser pulses
摘要： We have simulated the time evolution of the photon number distribution in a semiconductor quantum-dot–microcavity system driven by chirped laser pulses and compare with unchirped results. When phonon interactions with the dot are disregarded—thus corresponding to the limit of atomic cavity systems—chirped pulses generate photon number distributions that change their shape drastically in the course of time. Phonons have a strong and qualitative impact on the photon statistics. The asymmetry between phonon absorption and emission destroys the symmetry of the photon distributions obtained for positive and negative chirps. While for negative chirps transient distributions resembling thermal ones are observed, for positive chirps the photon number distribution still resembles its phonon-free counterpart but with overall smoother shapes. In sharp contrast, using unchirped pulses of the same pulse area and duration wave packets are found that move up and down the Jaynes-Cummings ladder with a bell shape that changes little in time. For shorter pulses and lower driving strength Rabi-like oscillations occur between low photon number states. For all considered excitation conditions transitions between sub- and super-Poissonian statistics are found at certain times. For resonant driving with low intensity the Mandel parameter oscillates and is mostly negative, which indicates a nonclassical state in the cavity ?eld. Finally, we show that it is possible that the Mandel parameter dynamically approaches zero and still the photon distribution exhibits two maxima and thus is far from being a Poissonian.
关键词： Mandel parameter,photon number distribution,chirped laser pulses,quantum-dot–cavity system,phonon interactions
更新于2025-09-23 15:21:01
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Synthesis of yttrium iron garnet/bismuth quantum dot heterostructures with localized plasmon enhanced magneto-optical performance
摘要： Interactions between light and magnetic matter attracted great attention lately due to their potential applications in nanophotonics, spintronics, and high-accuracy sensing. Here, we grew bismuth quantum dots (Bi–QDs) with strong spin–orbit coupling on a magnetic insulator yttrium iron garnet (YIG) via molecular beam epitaxy. The YIG/Bi–QDs material shows an enhanced magneto-optical Kerr rotation up to 130 % compared with that of a bare YIG film. The Bi–QDs were also introduced onto a lutetium–bismuth co-doped YIG film to form a hybrid system with remarkably enhanced Kerr rotation (from 1626 to 2341 mdeg). Ferromagnetic resonance measurements showed an increased effective magnetization as well as interfacial spin–orbit field in the YIG/Bi–QD heterostructures. Localized plasmons were mapped using electron energy loss spectroscopy with high spatial resolution, revealing enhanced plasmon intensity at both the Bi–QD surface and YIG/Bi–QD interface. Introducing Bi-QDs onto the YIG film enhanced Kerr rotation owing to the attenuated optical reflection and increased effective magnetization. The Bi–QD-enhanced magneto-optical effect enables development of efficient nanoscale light switching, spintronics, and even plasmonic nano-antennas.
关键词： Electron energy loss spectroscopy,Surface plasmon resonance,Bismuth quantum dot,Ferromagnetic resonance,Magneto-optical materials
更新于2025-09-23 15:21:01
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Impact of transition metal ion doping on electron spin relaxation time in CdSe/ZnSe quantum dots
摘要： Theoretical calculations of spin relaxation time (SRT) of conduction electrons have been carried out considering the relaxation mediated by acoustic phonons using k.p perturbation theory and envelope function approximation in a transition metal doped II-VI semiconductor quantum dot under the strong con?nement regime. In this calculation, we are considering the transitions in the Zeeman sublevels arising due to magnetic impurity doping and applied magnetic ?eld in a Mn doped CdSe/ZnSe quantum dots. The occurrence of spin polarization switching at moderately low applied magnetic ?eld is established in Cd1(cid:1)xMnxSe/ZnSe quantum dots. The spin relaxation times have been found to be considerably longer with a higher dopant concentration in small magnetic ?elds (B < 2T) and at very low temperature (T < 50 K) regime. The results may help to demonstrate that, such small quantum dots can successfully be used as polarization switch in different spintronic nano-device.
关键词： Quantum dot,Electronic structure,Spin relaxation,Spintronics,Semiconductor
更新于2025-09-23 15:21:01
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Improvement of Power Conversion Efficiency of Quantum Dot-Sensitized Solar Cells by Doping of Manganese into a ZnS Passivation Layer and Cosensitization of Zinc-Porphyrin on a Modified Graphene Oxide/Nitrogen-Doped TiO <sub/>2</sub> Photoanode
摘要： It is vital to acquire power conversion efficiencies comparable to other emerging solar cell technologies by making quantum dot-sensitized solar cells (QDSSCs) competitive. In this study, the effect of graphene oxide (GO), nitrogen, manganese, and a porphyrin compound on the performance of QDSSCs based on a TiO2/CdS/ZnS photoanode was investigated. First, adding GO and nitrogen into TiO2 has a conspicuous impact on the cell efficacy. Both these materials reduce the recombination rate and expand the specific surface area of TiO2 as well as dye loading, reinforcing cell efficiency value. The maximum power conversion efficiency of QDSSC with a GO N-doped photoelectrode was 2.52%. Second, by employing Mn2+ (5 and 10 wt %) doping of ZnS, we have succeeded in considerably improving cell performance (from 2.52 to 3.47%). The reason for this could be for the improvement of the passivation layer of ZnS by Mn2+ ions, bringing about to a smaller recombination of photoinjected electrons with either oxidized dye molecules or electrolyte at the surface of titanium dioxide. However, doping of 15 wt % Mn2+ had an opposite effect and somewhat declined the cell performance. Finally, a Zn-porphyrin dye was added to the CdS/ZnS by a cosensitization method, widening the light absorption range to the NIR (near-infrared region) (>700 nm), leading to the higher short-circuit current density (JSC) and cell efficacy. Utilizing an environmentally safe porphyrin compound into the structure of QDSSC has dramatically enhanced the cell efficacy to 4.62%, which is 40% higher than that of the result obtained from the TiO2/CdS/ZnS photoelectrode without porphyrin coating.
关键词： graphene oxide,nitrogen doping,manganese doping,quantum dot-sensitized solar cells,cosensitization,Zn-porphyrin,power conversion efficiency
更新于2025-09-23 15:21:01
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Fluorescence resonance energy transfer (FRET) between acriflavine and CdTe quantum dot
摘要： In this report we have studied Fluorescence Resonance Energy Transfer between Acri?avine (Acf) and Cadmium Telluride (CdTe) quantum dot. CdTe quantum dots were synthesized by hydrothermal method. Spectroscopic characterizations revealed the formation of a FRET pair consisting of Acri?avine (AcF) as donor and CdTe quantum dot as acceptor having energy transfer ef?ciency 39.5%.
关键词： Quantum dot,XRD,CdTe,FRET
更新于2025-09-23 15:21:01
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Analyzing role of relaxation time on second harmonic generation and optical dielectric function of impurity doped quantum dots under the aegis of noise
摘要： Present study monitors the influence of relaxation time (τ) on second harmonic generation (SHG) and total optical dielectric function (TODF) of impurity containing quantum dot (QD) under the stewardship of Gaussian white noise. Two distinct roadways viz. ‘additive’ and ‘multiplicative’ have been exploited for the entrance of noise to the system. Both in absence and presence of noise the SHG and TODF peak positions do not exhibit any shift with increase in τ. The SHG peak values display monotonic behavior with the variation of τ. However, the TODF peak values delicately depend on variation of τ being guided by the presence of noise and also on its mode of introduction. Presence of additive (multiplicative) noise causes enhancement (suppression) of SHG and TODF peak values as τ varies over a range. The findings appear to be crucial in the fabrication of QD-based opto-electronic devices where role of noise deserves to be properly addressed.
关键词： Quantum dot,Gaussian white noise,Impurity,Total optical dielectric function,Relaxation time,Second harmonic generation
更新于2025-09-23 15:21:01
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Optical vibration modes in multi-layer quantum dots of polar ternary mixed crystals
摘要： Within the framework of the dielectric continuum approach and the modified random-element isodisplacement model, the optical vibration modes as well as the corresponding electron-phonon interactions in spherical multi-layer quantum dots (QDs) consisting of ternary mixed crystals (TMCs) are investigated in detail. The dispersion relation and electron-phonon interaction Hamiltonian are obtained. As applications of the present theory, the numerical calculations for the ZnS/ZnxCd1-xS/ZnS and GaAs/AlxGa1-xAs/GaAs QDs are performed and discussed. Considering the "one-mode" and "two-mode" behaviors of the TMCs, the results show that there are 5 and 7 branches of interface/surface optical (IO/SO) phonon modes in the two systems, respectively. It is found that the effects of TMCs have a remarkable influence on the optical phonon frequencies and the electron-phonon interactions. The results also reveal that the presence of the cap layer introduces significant influence on the TMCs effects of optical phonon in multi-layer QDs. We hope that our theoretical results can stimulate further investigations of related photoelectric properties, as well as device applications in multi-layer QDs consisting of TMCs.
关键词： ternary mixed crystal,electron-phonon interaction,optical vibration mode,multi-layer quantum dot
更新于2025-09-23 15:21:01