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Interdisciplinary Collaborations to Address the Uncertainty Problem in Life Cycle Assessment of Nano-enabled Products: Case of the Quantum Dot-enabled Display
摘要： Life Cycle Assessment (LCA) is a powerful tool for assessing the environmental impacts of established processes and products. However, its use in decision-making for sustainable development of emerging technologies is challenging. High levels of uncertainty and lack of data over the complete value chain associated with nascent nano-enabled products (NEPs) makes it difficult to perform LCA studies early in the design process. This study addresses the uncertainty problem faced by LCA, and a demonstration is performed with a case study of quantum dot (QD)-enabled display. The study at hand proposes a dynamic life cycle assessment (dLCA) framework, which emphasizes iterative evaluation and collaborative efforts to tackle the data scarcity problem faced by retrospective (traditional) LCA. Experimental study of two commercially available QD-enabled displays (hand-held tablet with CdSe QD-enabled display and TV set with InP QD-enabled display) is performed for data collection of QD amount and release. After complete digestion, the experimental result shows that the concentration of CdSe (3.92 ± 0.32 μg/cm2) in the QD enhancement film (QDEF) of Tablet is comparable with the concentration of InP (3.56 ± 0.24 μg/cm2) in the QDEF of TV. After accounting for the experimental results, the second traversal of dLCA is performed, and it shows that cumulative energy demand (CED) per unit area for InP QD-enabled displays is 5.28 x 10-3 MJ/cm2 (first traversal was 2.59 x 101 MJ/cm2) and CdSe QD-enabled displays is 3.92 x 10-4 MJ/cm2 (first traversal was 4.32 x 10-2 MJ/cm2). This study highlights the role of collaborative research between life cycle modelers and experimentalists to improve the credibility of LCA results for emerging NEPs. Even though this study is based on the case of QD-enabled displays, the proposed dLCA framework and interdisciplinary collaboration method can also be applied to other emerging technologies.
关键词： Quantum Dots,Environmental Impact,Life Cycle Assessment,Nano-enabled Products,Dynamic LCA
更新于2025-09-11 14:15:04
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Red‐Carbon‐Quantum‐Dot‐Doped SnO <sub/>2</sub> Composite with Enhanced Electron Mobility for Efficient and Stable Perovskite Solar Cells
摘要： An efficient electron transport layer (ETL) plays a key role in promoting carrier separation and electron extraction in planar perovskite solar cells (PSCs). An effective composite ETL is fabricated using carboxylic-acid- and hydroxyl-rich red-carbon quantum dots (RCQs) to dope low-temperature solution-processed SnO2, which dramatically increases its electron mobility by ≈20 times from 9.32 × 10?4 to 1.73 × 10?2 cm2 V?1 s?1. The mobility achieved is one of the highest reported electron mobilities for modified SnO2. Fabricated planar PSCs based on this novel SnO2 ETL demonstrate an outstanding improvement in efficiency from 19.15% for PSCs without RCQs up to 22.77% and have enhanced long-term stability against humidity, preserving over 95% of the initial efficiency after 1000 h under 40–60% humidity at 25 °C. These significant achievements are solely attributed to the excellent electron mobility of the novel ETL, which is also proven to help the passivation of traps/defects at the ETL/perovskite interface and to promote the formation of highly crystallized perovskite, with an enhanced phase purity and uniformity over a large area. These results demonstrate that inexpensive RCQs are simple but excellent additives for producing efficient ETLs in stable high-performance PSCs as well as other perovskite-based optoelectronics.
关键词： electron transport layers,SnO2,planar perovskite solar cells,synchrotron-based GIXRD,red-carbon quantum dots
更新于2025-09-11 14:15:04
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Photoluminescence properties as a function of growth mechanism for GaSb/GaAs quantum dots grown on Ge substrates
摘要： In this work, we use photoluminescence (PL) spectroscopy to investigate how self-assembled GaSb/GaAs quantum dots (QDs) depend on their growth mechanism. Carrier transfer (i.e., carrier recombination in QDs and escape through the barrier layer) is investigated as a function of excitation-power- and temperature-dependent PL measurements. A drastic blueshift of the QD peak energy from 1.23 to 1.30 eV and a further shift to 1.33 eV reveal the influence of the GaSb growth rate and the growth temperature on the optical properties of these QDs. The thermal activation energy is extracted from the temperature-dependent PL by fitting the integrated PL intensity of the QD peaks to the Arrhenius relation. The QDs grown at the growth rate of 0.1 monolayers/s at 450 °C have higher thermal activation energy (109 meV) than those grown at a lower growth rate and higher QD growth temperature. The observed PL characteristics are discussed in terms of QD size, uniformity of QDs, and material intermixing occurring during QD growth on the buffer layer and capping layer.
关键词： Ge substrates,quantum dots,photoluminescence,GaSb/GaAs,growth mechanism
更新于2025-09-11 14:15:04
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Fluorescence ON-OFF switching, Boolean logic gates like behavior of carbon quantum dots and highly sensitive bovine serum albumin sensing
摘要： We demonstrate ?uorescence “ON-OFF” switching and photonic logic gates based on ?uorescence response of carbon quantum dots (CQDs) in the presence of graphene oxide (GO), reduced graphene oxide (RGO), and bovine serum albumin (BSA). We study the excited state electron and energy transfer interactions among the carbon based materials in detail through steady state ?uorescence (SSF) and time resolved ?uorescence (TRF) spectroscopy. CQDs function as donor; GO and RGO function as acceptors. SSF results show the ?uorescence “turn-OFF” behavior of CQDs in the presence of GO and RGO, and the reason is explained through Stern-Volmer plots. TRF results reveal a decrease in the decay time components of CQDs in the presence of GO and RGO. The gradual recovery of quenched ?uorescence of CQDs is observed by the addition of BSA at nanomolar concentrations which shows the highly sensitive “turn-ON” BSA sensing. Single input and two inputs photonic logic gates are implemented based on the ?uorescence response of CQDs in the presence of GO, RGO, and BSA in di?erent input combinations. The NOT, PASS1, NOR, and IMPLICATION gates like behavior of CQDs is demonstrated.
关键词： bovine serum albumin sensing,fluorescence ON-OFF switching,carbon quantum dots,Boolean logic gates
更新于2025-09-11 14:15:04
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Systematic control of the rate of singlet fission within 6,13-diphenylpentacene aggregates with PbS quantum dot templates
摘要： Lead chalcogenide quantum dots (QDs) are promising acceptors for photovoltaic devices that harness the singlet fission (SF) mechanism. The rate of singlet fission of polyacenes in the presence of QDs is a critical parameter in determining the performance of such devices. The present study demonstrates that the rates of SF in a pentacene derivative, 6,13-dipenylpentacene (DPP), are modulated by forming coaggregates with PbS QDs in aqueous dispersions. PbS QDs generally accelerate SF within DPP aggregates, and the extent of acceleration depends on the size of the QD. The average rate of SF increases from 0.074 ps-1 for DPP-only aggregates to 0.37 ps-1 within DPP-D co-aggregates for QDs with radius 2.2 nm, whereas co-aggregation with the smallest (r = 1.6 nm) and largest (r = 2.7 nm) QDs we tried only slightly change the SF rate. The rate variation is associated with (i) the density of surface ligands, which is influenced by the faceting of the PbS surface, and (ii) the local dielectric constant for the DPP. To accelerate SF, the ligands should be dense enough to provide sufficient affinity for DPP aggregates and effectively perturb the perpendicular alignment of DPP monomers within aggregates to increase the intermolecular coupling that promotes SF, but should not be too dense so as to form a low dielectric environment that disfavors SF. The study suggests that it is critical to consider the influence of the microenvironment of QD surface on photophysical processes when fabricating QD/organic hybrid devices.
关键词： pentacene,photovoltaic devices,PbS,quantum dots,singlet fission
更新于2025-09-11 14:15:04
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Wurtzite InGaN/GaN Quantum Dots for Intermediate Band Solar Cells
摘要： Wurtzite InGaN quantum dots in GaN are investigated for intermediate band solar cells. A global limiting power conversion ef?ciency of 44% is predicted through detailed balance calculations with full freedom of allowed subgap transitions. We consider cylindrical quantum dots, predicting band structures using an 8-band k.p model, including deformation potential and piezoelectric ?elds from induced lattice strain. Taking the energy levels from the k.p model as absorption cutoffs in the detailed balance calculation, we determine the best device ef?ciency possible as a function of indium fraction and dot size. For small dots, of size ≈ 50 ?A and indium fraction ≈ 0.7, ef?ciencies up to 42% are in principle attainable under 1-sun illumination.
关键词： Quantum Dots,Intermediate Band Solar Cells,Detailed Balance Calculations,8-band k.p model,Wurtzite InGaN
更新于2025-09-11 14:15:04
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Carbon quantum dots derived by direct carbonization of carbonaceous microcrystals in mesophase pitch
摘要： Aggregation of the central aromatic ring system of asphaltene molecules due to π–π interaction can lead to the formation of carbon quantum dots (CQDs). However, to date, such a roadmap has not been demonstrated. Here, we present a simple approach to the synthesis of CQDs by direct carbonization of dispersed carbonaceous microcrystals in mesophase pitch. The size of the as-prepared CQDs is modulated by adjusting the nucleation temperature for mesophase formation. Due to the oxygen-free character, the CQDs exhibit excitation-independent fluorescent behavior with a quantum yield up to 87%. The CQDs were successfully applied to fluorescent detection of Fe3+ ions with good specificity and sensitivity. Our results not only provide a scalable production of CQDs at low cost, but also give valuable clues to understand the solidification of asphaltene at nanoscale.
关键词： Fe3+ ions,carbonization,mesophase pitch,fluorescent detection,carbon quantum dots
更新于2025-09-11 14:15:04
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<i>In situ</i> fabrication of a direct <i>Z</i> -scheme photocatalyst by immobilizing CdS quantum dots in the channels of graphene-hybridized and supported mesoporous titanium nanocrystals for high photocatalytic performance under visible light
摘要： We report the considerable advantages of direct Z-scheme photocatalysts by immobilizing high-quality CdS quantum dots (QDs) in the channels of graphene-hybridized and supported mesoporous titania (GMT) nanocrystals (CdS@GMT/GR) under facile hydrothermal conditions. The photocatalysts have been characterized by XRD, PL, XPS, SEM, DRS, TEM, EIS, and N2 adsorption. CdS QDs primarily serve as photosensitizers with a unique pore-embedded structure for the e?ective utilization of the light source. This direct Z-scheme CdS@GMT/GR exhibits higher photocatalytic activity than CdS/GR, GMT/GR, or CdS@MT. In addition, the rate constant of CdS@GMT/GR-2 is approximately twice the sum of those of CdS@MT and GMT/GR, because GR played the role of hole-transporting and collection layer as well as the hybridization level formation in terms of hybridizing MT and serving as a support. Therefore, the GR content tunes the energy band, a?ects the surface area, and controls the interfacial hole transfer and collection rate of the direct Z-scheme system. Furthermore, CdS@GMT/GR retains its high performance in repeated photocatalytic processes. This can be attributed to the fact that GR prevents QDs from photocorrosion by means of the hole-transporting and collection e?ect. A possible reaction mechanism is proposed. This work provides a promising strategy for the construction of highly e?cient visible-light-driven photocatalysts to reduce the growing menace of environmental pollution.
关键词： environmental pollution,visible-light-driven photocatalysts,graphene-hybridized mesoporous titania,direct Z-scheme photocatalysts,CdS quantum dots
更新于2025-09-11 14:15:04
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SnS <sub/>2</sub> quantum dots: Facile synthesis, properties, and applications in ultraviolet photodetector
摘要： Tin sulfide quantum dots (SnS2 QDs) are n-type wide band gap semiconductor. They exhibit a high optical absorption coefficient and strong photoconductive property in the ultraviolet and visible regions. Therefore, they have been found to have many potential applications, such as gas sensors, resistors, photodetectors, photocatalysts, and solar cells. However, the existing preparation methods for SnS2 QDs are complicated and require a high temperature and high pressure environments; hence they are unsuitable for large-scale industrial production. An effective method for the preparation of monodispersed SnS2 QDs at normal temperature and pressure will be discussed in this paper. The method is facile, green, and low-cost. In this work, the structure, morphology, optical, electrical, and photoelectric properties of SnS2 QDs are studied. The synthesized SnS2 QDs are homogeneous in size and exhibit good photoelectric performance. A photoelectric detector based on the SnS2 QDs is fabricated and its J–V and C–V characteristics are also studied. The detector responds under λ = 365 nm light irradiation and reverse bias voltage. Its detectivity approximately stabilizes at 1011 Jones at room temperature. These results show the possible use of SnS2 QDs in photodetectors.
关键词： photodetector,photoelectric properties,quantum dots,SnS2
更新于2025-09-11 14:15:04
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Highly photo-stable CsPbI3 perovskite quantum dots via thiol ligand exchange and their polymer film application
摘要： Highly photo-stable CsPbI3 perovskite quantum dots (PeQDs) were prepared using thiol as an exchanged ligand. Photoluminescence of CsPbI3 perovskite quantum dots can be maintained for a long time in UV via thiol ligand exchange. As an application, perovskite films were fabricated using the PeQDs and a cyclic olefin copolymer (COC). The thiol-treated PeQD films exhibited higher stability than the untreated films under irradiation with a blue light-emitting diode (LED).
关键词： thiol-capped CsPbI3 perovskite quantum dots,photo-stability,QD films,Ligand exchange
更新于2025-09-11 14:15:04