- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Manipulation of Phase-Transfer Ligand-Exchange Dynamics of PbS Quantum Dots for Efficient Infrared Photovoltaics
摘要： Chemical surface treatment of colloidal quantum dots (CQDs) by phase-transfer ligand exchange (PTLE) is essential to implement highly densified, well-passivated CQD films for optoelectronic applications, such as infrared photovoltaics, light-emitting diodes and photodetectors. The PTLE, however, involves parallel and interactional processes of ligand exchange, phase transfer, and surface passivation of CQDs, which renders the optimization of PTLE still challenging. Herein, we explored the action mechanism of a widely-used additive, ammonium acetate (AA), on the PTLE of PbS CQDs in order to recognize the dynamic balance during the PTLE process and its impact on the performance of colloidal quantum dot solar cells (CQDSCs). Our research definitely shows that AA additive can modify the dynamics of PTLE by participating in all the three processes, and the amount of AA significantly influences the defect passivation and colloidal stability of PbS CQDs. At an appropriate concentration (~50 mM) of AA, PbS CQDs are well iodide-passivated by the PTLE, and the fabricated CQDSCs achieve the PCE of ~10% associated with the improved carrier transport and the reduced trap-assisted carrier recombination. However, excessive AA causes the trace residual AA on the CQD surface, resulting in the insufficient surface passivation of PbS CQDs and trap issues of CQDSCs. The double-edged sword effect of AA additive on the PTLE, demonstrated in our work, suggests that realizing the dynamic balance of different processes during PTLE is crucial for the further performance promotion of CQDSCs.
关键词： infrared photovoltaics,ammonium acetate,phase-transfer ligand exchange,colloidal quantum dots,surface passivation
更新于2025-09-11 14:15:04
-
Surface Modification for Improving the Photocatalytic Polymerization of 3,4-Ethylenedioxythiophene over Inorganic Lead Halide Perovskite Quantum Dots
摘要： Inorganic lead halide perovskite quantum dots (iLHP-QDs) have recently been used in the photocatalytic reaction. However, the factors that influence the photocatalytic performance of the iLHP-QDs has not been fully investigated. Herein, we synthesised a series of iLHP-QDs with varied halide ratio (CsPbX3, X=I, I0.67Br0.33, I0.5Br0.5, I0.33Br0.67, Br) and studied its influence on the photocatalytic performance by monitoring the polymerization of TerEDOT. The CsPbI3 QDs showed the best performance owing to its narrow bandgap and low exciton binding energy. Moreover, the photocatalytic performance of the iLHP-QDs could be simply improved by being treated with methyl acetate, which can be attributed to the replacement of the oleic acid by the short acetate acid, and the introduction of the traps on the surface of QDs in the post-treatment. These results could help design more efficient photocatalytic system and further promote the application of iLHP-QDs.
关键词： photocatalytic performance,quantum dots,exciton binding energy,charge transport efficiency,halide perovskite
更新于2025-09-11 14:15:04
-
p-GaN/n-ZnO Nanorod/CsPbBr <sub/>3</sub> Quantum Dots Decorated with ZnO Nanoseeds for Light-Emitting Diodes
摘要： In this paper, we report the dual-wavelength green-light emission from zinc oxide (ZnO)-nanoseed-decorated p-GaN (gallium nitride)/n-ZnO nanorod/CsPbBr3 quantum dots (QDs) light-emitting diodes (LEDs). At the same time, the effect of ZnO nanoseeds on the p-GaN/n-ZnO nanorod/CsPbBr3 QDs LED performance is deeply studied. ZnO nanoseeds were fabricated by magnetron sputtering and the sol?gel method; then ZnO nanorods were obtained on GaN by hydrothermal treatment to form the p-GaN/n-ZnO nanorod heterojunction, and green CsPbBr3 QDs were further deposited on ZnO nanorod arrays to realize LEDs. The results show that magnetron-sputtering ZnO nanoseeds can induce regular vertical ZnO nanorod arrays, and the corresponding device presents a better electroluminescence (EL) performance. The X-ray diffraction, atomic force microscopy, and EL mechanisms indicate that the p-GaN/n-ZnO nanorod with magnetron-sputtering ZnO nanoseeds has a better crystalline interface. Our results indicate that the p-GaN/n-ZnO nanorod/CsPbBr3 QDs heterojunction structure can be served as dual-wavelength LEDs, and magnetron-sputtering ZnO nanoseeds can give rise to a better EL performance.
关键词： CsPbBr3 quantum dots,electroluminescence,ZnO nanoseeds,ZnO nanorods,light-emitting diodes
更新于2025-09-11 14:15:04
-
Efficient hybrid colloidal quantum dot/organic solar cells mediated by near-infrared sensitizing small molecules
摘要： Solution-processed semiconductors are promising materials to realize optoelectronic devices that combine high performance with inexpensive manufacturing. In particular, the exploitation of colloidal quantum dots (CQDs) capable of harvesting infrared photons, in conjunction with visible-absorbing organic chromophores, has been demonstrated as an interesting route. Unfortunately, CQD/organic hybrid photovoltaics have been limited to power conversion efficiencies (PCEs) below 10% due to chemical mismatch and difficulties in facilitating charge collection. Here we devise a hybrid architecture that overcomes these limitations by introducing small molecules into the CQD/organic stacked structure. The small molecule complements CQD absorption and creates an exciton cascade with the host polymer, thus enabling efficient energy transfer and also promoting exciton dissociation at heterointerfaces. The resulting hybrid solar cells exhibit PCEs of 13.1% and retain over 80% of their initial PCE after 150?h of continuous operation unencapsulated, outperforming present air-processed solution-cast CQD/organic photovoltaics.
关键词： hybrid photovoltaics,organic solar cells,small molecules,power conversion efficiency,colloidal quantum dots
更新于2025-09-11 14:15:04
-
Uniform-Sized Indium Quantum Dots Grown on the Surface of an InGaN Epitaxial Layer by a Two-Step Cooling Process
摘要： A new method to grow Indium quantum dots (In QDs) on the surface of an epitaxial InGaN layer by MOCVD is proposed. Uniform-sized In quantum dots have been found to form on the surface of an InGaN layer when a two-step cooling process is taken. Through analyzing, we found that the formation of In QDs on the surface is due to the reaction between the surface In-rich layer and the carrier gas H2 at the lower temperature period in the two-step cooling process. At the same time, as the density of In QDs is closely dependent on the surface In-rich layer, this provides us a way to study the surface property of the InGaN layer directly.
关键词： In quantum dots,Single InGaN layer,In-rich layer
更新于2025-09-11 14:15:04
-
One-step hydrothermal synthesis of silver-doped carbon quantum dots for highly selective detection of uric acid
摘要： In this paper, a simple and convenient fluorescence method for detection of uric acid (UA) based on Ag-doped carbon quantum dots (Ag-CQDs) is developed. The Ag-CQDs contain Ag species could bond with UA, which promoted the electron and/or energy transfer and produced high quenching extent. Thus, the fluorescence intensity of Ag-CQDs decreased in the presence of UA. Under the optimal condition, the UA sensor exhibited a linear response in the range of 0.005-100 μM with a detection limit of 0.35 nM (S/N=3). Ag-CQDs demonstrated high sensitivity and rapid response to UA over a wide range of concentration indicating their great potential as a fluorescent probe for chemical sensing. Moreover, this method has successfully applied to detect UA in human urine samples.
关键词： silver,doping,carbon quantum dots,uric acid,fluorescence
更新于2025-09-11 14:15:04
-
Quantum dots of molybdenum nitride embedded in continuously distributed polyaniline as novel electrode material for supercapacitor
摘要： Molybdenum nitride (Mo2N) and molybdenum nitride/polyaniline composites (Mo2N@PANI) have been prepared by simple static precipitation and in situ growth methods. The morphological and structural properties and chemical composition of the prepared materials have been analyzed by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The obtained results illustrate that in molybdenum nitride/polyaniline composites, polyaniline has been allocate continuously embedded with the quantum dots of molybdenum. Therefore, the formation of quantum dots of molybdenum and its uniform distribution in polyaniline bulk suggested that the synthesized materials could be used as an electrode material of supercapacitors. From the results of electrochemical analysis, the mass ratio capacitance of molybdenum nitride/polyaniline composites have been found to be 111.8 F/g at 0.5 A/g, while the mass ratio capacitance of pure molybdenum nitride is only 47.5 F/g at the same current density. Hence, obtained results clearly con?rm that molybdenum nitride/polyaniline composites nanostructured quantum dot material is one of the best and novel electrode materials for high performed supercapacitors which exhibits excellent electrochemical properties.
关键词： Electrode materials,Supercapacitor,Molybdenum nitride,Polyaniline,Quantum dots
更新于2025-09-11 14:15:04
-
Influence of the Cation on the Surface Electronic Band Structure and Magnetic Properties of Mn:ZnS and Mn:CdS Quantum Dot Thin Films
摘要： The effects of doping Mn into ZnS and CdS quantum dots are reported. Scanning tunneling spectroscopy spectra show a reduction in the electronic band gap in both CdS and ZnS upon incorporation of the Mn dopant. Mn:ZnS exhibits a rigid band shift toward higher bias which is reminiscent of a hole doping effect. This rigid band shift in Mn:ZnS is argued, with the help of X-ray photoelectron spectroscopy, to be due to a hole-doping mechanism caused by the favorable formation of Zn vacancies and a reduction in S vacancies compared to undoped ZnS films. In CdS no rigid band shift is observed even though the presence of Cd vacancies can be confirmed by photoemission and magnetic measurements. A strong sp-d hybridization is observed in the Mn:CdS film upon introducing the Mn dopant. d0 ferromagnetism is observed in both undoped ZnS and CdS quantum dot thin films at room temperature. Upon doping of Mn into ZnS the magnetization is reduced suggesting an antiparallel alignment of Mn-Mn or Mn-Zn vacancies nearest neighbors. Density Functional Theory supports the experimental results indicating the nearest neighbor Mn atoms prefer antiparallel alignment of their magnetic moments with preferred ground state of Mn in 3+ oxidation state.
关键词： CdS,Mn doping,quantum dots,magnetic properties,scanning tunneling spectroscopy,electronic band structure,X-ray photoelectron spectroscopy,density functional theory,ZnS
更新于2025-09-11 14:15:04
-
Enhancing Nonradiative Energy Transfer between Nitridized Carbon Quantum Dots and Monolayer WS2
摘要： Two-dimensional (2D) monolayer (1L) transition metal dichalcogenides (TMDs) suffer from a low absorption in the visible light region. Nonradiative energy transfer (NRET) is an effective method to enhance such absorption, which, as shown in this study, can be accomplished by using surface nitridized carbon quantum dots (CQDs). The optical absorption and photoluminescence (PL) of CQDs in the visible light region can be greatly enhanced by increasing the level of nitridization. The nitridized CQDs exhibit weak p-type doping but strong PL quenching in contact with vapor transport (VT)-deposited 1L-WS2. Owing to the good overlap between the fluorescence and absorption spectra for CQDs and 1L-WS2, an interactive NRET process reduces the PL lifetimes of both CQDs and 1L-WS2. The NRET efficiency can be greatly enhanced by up to 73% for samples coated with CQDs of increasing surface nitridization.
关键词： Nonradiative energy transfer,Nitridized carbon quantum dots,Optical absorption,Monolayer WS2,Photoluminescence
更新于2025-09-11 14:15:04
-
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