A5060941410- Quantum Dots Synthesis And Properties
- Chalcogenide Semiconductor Thin Films
- TiO2 Photocatalysis and Solar Cells
- Photochemistry and Electron Transfer Studies
- Copper-based nanomaterials and applications
- Advanced Photocatalysis Techniques
- ZnO doping and properties
- Light effects on plants
- Perovskite Materials and Applications
- Semiconductor Quantum Structures and Devices
- Nanowire Synthesis and Applications
- Quantum Chromodynamics and Particle Interactions
- Electromagnetic Scattering and Analysis
- Numerical methods in inverse problems
- solar cell performance optimization
- Organic Light-Emitting Diodes Research
- Thermal Radiation and Cooling Technologies
- Luminescence Properties of Advanced Materials
- Advanced Semiconductor Detectors and Materials
- Electronic and Structural Properties of Oxides
- Nonlinear Optical Materials Studies
- Photonic and Optical Devices
- Particle physics theoretical and experimental studies
- Iron oxide chemistry and applications
- Glass properties and applications
UbiQD (United States)
2015-2025
Los Alamos National Laboratory
2013-2017
University of Illinois Urbana-Champaign
1972-2012
University of Chicago Medical Center
1972
University of Illinois Chicago
1972
Illinois Institute of Technology
1969
Development of light-emitting diodes (LEDs) based on colloidal quantum dots is driven by attractive properties these fluorophores such as spectrally narrow, tunable emission and facile processibility via solution-based methods. A current obstacle towards improved LED performance an incomplete understanding the roles extrinsic factors, non-radiative recombination at surface defects, versus intrinsic processes, multicarrier Auger or electron-hole separation due to applied electric field. Here...
The influence of a CdSexS1-x interfacial alloyed layer on the photophysical properties core/shell CdSe/CdS nanocrystal quantum dots (QDs) is investigated by comparing reference QDs with sharp interface to structures an intermediate at interface. To fully realize structural contrast, we have developed two novel synthetic approaches: method for fast CdS-shell growth, which results in abrupt boundary (no intentional or unintentional alloying), and depositing alloy controlled composition onto...
Solution-processed semiconductor quantum dot solar cells offer a path towards both reduced fabrication cost and higher efficiency enabled by novel processes such as hot-electron extraction carrier multiplication. Here we use new class of low-cost, low-toxicity CuInSexS2−x dots to demonstrate sensitized with certified efficiencies exceeding 5%. Among other material device design improvements studied, methanol-based polysulfide electrolyte results in particularly dramatic enhancement...
Building-integrated sunlight harvesting utilizing laminated glass luminescent solar concentrators (LSCs) is proposed. By incorporating high quantum yield (>90%), NIR-emitting CuInS2/ZnS dots into the polymer interlayer between two sheets of low-iron float glass, a record optical efficiency 8.1% demonstrated for 10 cm × device that transmits ∼44% visible light. After completing prototypes by attaching silicon cells along perimeter device, electrical power conversion was certified at 2.2% with...
Luminescent solar concentrators (LSCs) can be utilized as both large-area collectors of radiation supplementing traditional photovoltaic cells well semitransparent "solar windows" that provide a desired degree shading and simultaneously serve power-generation units. An important characteristic an LSC is concentration factor (C) thought coefficient effective enlargement (or contraction) the area cell when it coupled to LSC. Here we use analytical numerical Monte Carlo modeling in addition...
Colloidal CuInSexS2-x quantum dots (QDs) are an attractive less-toxic alternative to PbX and CdX (X = S, Se, Te) QDs for solution-processed semiconductor devices. This relatively new class of QD materials is particularly suited serving as absorber in photovoltaics, owing its high absorption coefficient near-optimal finely tunable band gap. Here, we engineer sensitizers enhanced performance QD-sensitized TiO2 solar cells (QDSSCs). Our synthesis employs 1-dodecanethiol (DDT) a low-cost...
Luminescent CuInS2 (CIS) quantum dots (QDs) exhibit highly efficient intragap emission and long, hundreds-of-nanoseconds radiative lifetimes. These spectral properties, distinct from structurally similar II–VI QDs, can be explained by the involvement of defect states containing a localized hole capable coupling with conduction band electron for transition. However, absolute energies band-edge states, structure emissive defect(s), role origin nonemissive decay channels still remain poorly...
Abstract Bioregenerative life-support systems (BLSS) involving plants will be required to realize self-sustaining human settlements beyond Earth. To improve plant productivity in BLSS, the quality of solar spectrum can modified by lightweight, luminescent films. CuInS 2 /ZnS quantum dot (QD) films were used down-convert ultraviolet/blue photons red emissions centered at 600 and 660 nm, resulting increased biomass accumulation romaine lettuce. All growth parameters, except for spectral...
Common approaches to synthesizing alloyed CuInSexS2–x quantum dots (QDs) employ high-cost, air-sensitive phosphine complexes as the selenium precursor. Such methods typically offer low chemical yields and only moderate emission efficiencies, particularly for selenium-rich compositions. Here we demonstrate that such hazardous precursors can be completely avoided by utilizing a combination of thiols amines is very effective at reducing then complexing with elemental form highly reactive...
High-quality epitaxial interfaces and delicate control over shape anisotropy make nanorod heterostructures (NRHs) with staggered band offsets efficient in separating directing photogenerated carriers. Combined versatile scalable wet chemical means of synthesis, these salient features NRHs are useful for improving both the performance cost-effectiveness photovoltaics (PVs). However, inefficient carrier transport extraction have imposed severe limitations, outweighing benefits enhanced charge...
We compare the absorption, photoluminescence, and magneto-optical properties of colloidal CuInS2 (CIS) nanocrystals with two closely related well-understood binary analogs: Cu-doped ZnSe CdSe nanocrystals. In contrast conventional CdSe, both CIS exhibit a substantial energy separation between emission absorption peaks (Stokes shift) marked asymmetry in polarization-resolved low-temperature magneto-photoluminescence, which point to role localized dopant/defect states forbidden gap....
Ternary CuInS2 nanocrystals (CIS NCs) are attracting attention as nontoxic alternatives to heavy metal–based chalcogenides for many technologically relevant applications. The photophysical processes underlying their emission mechanism are, however, still under debate. Here we address this problem by applying, the first time, spectro-electrochemical methods core-only CIS and core/shell CIS/ZnS NCs. application of an electrochemical potential enables us reversibly tune NC Fermi energy thereby...
CuInS2 (CIS) quantum dots (QDs) have emerged as one of the most promising candidates for application in a number new technologies, mostly due to their heavy-metal-free composition and unique optical properties. Among those, large Stokes shift long-lived excited state are striking ones. Although these properties important, physical mechanism that originates them is still under debate. Here, we use two-photon absorption spectroscopy ultrafast dynamics studies investigate origin those...
While luminescent solar concentrators (LSCs) have been researched for several decades, there is still a lack of commercially available systems, mostly due to scalability, performance, aesthetics, or some combination these challenges. These obstacles can be overcome by the systematic optimization laminated glass LSC design, demonstrated herein. In particular, we first show that it possible improve optical and electrical efficiencies an fine-tuned constituent fluorophore-containing interlayer...
Core/shell nanostructures of type I and II band-offset materials have been pivotal in improving photoluminescence imparting charge separation well-established colloidal quantum dots. In addition to these features, the multishell motif provides a simple means expand emission spectral range spatially fine-tune electron hole wave functions. Here, we explore CdSe/CdTe/CdSe core/shell/shell structure with total diameter ≲7 nm, within practical limits readily accessible synthesis capabilities....
To better understand the growth mechanism leading to enhanced anisotropy in nanocrystal heterostructures synthesized from nearly spherical seeds, we have examined various factors that contribute structural diversification Fe3O4/CdS systems. Pseudoseparation of nucleation and allows us quantify how number heterojunctions formed varies with concentration size seed nanocrystals. A careful examination dependence maximum CdS particles can nucleate per suggests strain induced limitations. By...
Recent advances allowing high-quality epitaxial heterointerfaces and delicately controlled shape anisotropy combined with versatile scalable chemical synthesis make nanorod heterostructures (NRHs) appealing for various applications in photonics, electronics, photovoltaics. When two distinct semiconductor materials staggered band offsets are brought together a NRH, the type-II heterojunction formed between them is expected to promote efficient separation of photogenerated carriers, should...
Type-II nanorod heterostructures (NRHs) exhibit efficient directional charge separation and provide the potential to control this flow of charges through changes in structure composition. We use transient-absorption spectroscopy investigate how magnitude band offset lattice strain alters dynamics photogenerated electrons CdSe/CdTe type-II NRHs. In absence alloying effects, electron transfer occurs ∼300 fs. Reducing conduction by means leads an even shorter charge-separation time (<200 fs),...
CuInSexS2–x quantum dot field-effect transistors show p-type, n-type, and ambipolar behaviors with carrier mobilities up to 0.03 cm2 V–1 s–1. Although some design rules from studies of cadmium lead containing dots can be applied, remarkable differences are observed including a strong gating effect in as-synthesized nanocyrstals long ligands.
While luminescent concentrators (LCs) are mainly designed to harvest sunlight and convert its energy into electricity, the same concept can be advantageous in alternative applications. Examples of such applications demonstrated here by coupling edge-guided light high-performance LCs based on CuInSexS2-x/ZnS quantum dots optical fibers with emission covering visible-to-NIR spectral regions. In particular, a cost-efficient, miniature broadband source for medical diagnostics,...
Laminated-glass, luminescent solar concentrators (LSCs) offer localized and sustainable power generation combined with the customizable transparency needed for windows. Successful commercial deployment of LSC technology depends on demonstration economically viable efficiency, while maintaining excellent aesthetics. In this work, multiple-interlayer CuInS2/ZnS quantum dot (QD) devices comprised laminated glass are presented. Three-interlayer designs demonstrated a certified electrical...
The spectral quality of sunlight reaching plants remains a path for optimization in greenhouse cultivation. Quantum dots represent novel, emission-tunable luminescent material optimizing the spectrum greenhouses with minimal intensity loss, ultimately enabling improved light use efficiency plant growth without requiring electricity. In this study, films containing CuInS 2 /ZnS quantum were utilized to absorb and convert ultraviolet blue photons from photoluminescent emission centered at 600...
Type-II band-offset CdSe/CdTe nanorod heterostructures with curved and linear shapes have been synthesized examined atomic-resolution transmission electron microscopy techniques. Strain from growth of larger-lattice CdTe partly on the sides CdSe seeds is shown to lead an overall curvature in rods. Lattice expansion inner outer portion region exceeds expected lattice mismatch between two materials because buildup unusual compressive strain CdSe. In contrast, exclusive tip results...