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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Drift Transport in Al 2 O 3 -Sheathed 3-D Transparent Conducting Oxide Photoanodes Observed in Liquid Electrolyte-Based Dye-Sensitized Solar Cells

It has long been taken for granted that electron transport in liquid-electrolyte-based dye-sensitized solar cells (DSSCs) undergoes an ambipolar diffusive transport due to the strong coupling between electrons in the photoanode and the nearby mobile cations in liquid electrolyte, which, therefore, screens off any electric field in the photoanodes and consequently eliminates the possibility for drift transport. In this work, we demonstrate the existence of drift transport in liquid electrolyte-based DSSCs using a thin Al 2 O 3 -sheathed 3-dimentional (3-D) fluorinated tin oxide (FTO), as photoanodes. The electron diffusion rate in such 3-D TCO based DSSC exhibits a striking enhancement to the value of ~10 –2 cm 2 /s, about 10 4 times faster than that of the TiO 2 nanoparticle-based DSSCs. The electron diffusion coefficient is independent of the photoelectron density, while intensity modulated photocurrent spectroscopy (IMPS) suggests that the time constants of electron transport exhibit a linear dependence on the bias voltage, a strong indication of drift transport behavior in this 3-D FTO hollow nanobeads-based DSSC, despite the use of liquid I – /I 3 – electrolyte.

14 SOLAR ENERGY↗
DOE OSTI2018

Structural basis for activation of fluorogenic dyes by an RNA aptamer lacking a G-quadruplex motif

The DIR2s RNA aptamer, a second-generation, in-vitro selected binder to dimethylindole red (DIR), activates the fluorescence of cyanine dyes, DIR and oxazole thiazole blue (OTB), allowing detection of two well-resolved emission colors. Using Fab BL3-6 and its cognate hairpin as a crystallization module, we solved the crystal structures of both the apo and OTB-SO 3 bound forms of DIR2s at 2.0 Å and 1.8 Å resolution, respectively. DIR2s adopts a compact, tuning fork-like architecture comprised of a helix and two short stem-loops oriented in parallel to create the ligand binding site through tertiary interactions. The OTB-SO 3 fluorophore binds in a planar conformation to a claw-like structure formed by a purine base-triple, which provides a stacking platform for OTB-SO 3 , and an unpaired nucleotide, which partially caps the binding site from the top. The absence of a G-quartet or base tetrad makes the DIR2s aptamer unique among fluorogenic RNAs with known 3D structure.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Perovskite- and Dye-Sensitized Solar-Cell Device Databases Auto-generated Using ChemDataExtractor

The number of scientific publications reporting cutting-edge third-generation photovoltaic devices is increasing rapidly, owing to the pressing need to develop renewable-energy technologies that address the climate-change crisis. Consequently, the field could benefit from a central repository where photovoltaic-performance metrics, such as the power-conversion efficiency (η) are recorded. We present two automatically generated databases that contain photovoltaic properties and device material data for dye-sensitized solar cells (DSCs) and perovskite solar cells (PSCs), totalling 660,881 data entries representing 57,678 photovoltaic devices. The databases were generated by applying the text-mining toolkit ChemDataExtractor on a corpus of 25,720 articles. A multi-faceted evaluation, incorporating manual and automatic methods, was applied to ensure that the data contained therein were of the highest quality, with precision metrics ranging from 73.1% to 95.8%. The DSC database contains 475,045 entries representing 41,680 devices, and the PSC database contains 185,836 entries representing 15,818 devices. The databases are available in MongoDB and JSON formats, which can be queried in Python, R, Java and MATLAB for data-driven photovoltaic materials discovery.

14 SOLAR ENERGY↗
DOE OSTI2014

Encapsulation of large dye molecules in hierarchically superstructured metal–organic frameworks

Microporous metal–organic frameworks (MOFs) represent a new family of microporous materials, offering potential applications in gas separation and storage, catalysis, and membranes. We expect that the engineering of hierarchical superstructured MOFs, i.e., fabricating mesopores in microporous frameworks during the crystallization stage will serve a myriad of applications for molecular adsorption, drug delivery, and catalysis. But, MOFs with mesopores are rarely studied because of the lack of a simple, effective way to construct mesoscale cavities in the structures. We report the use of a perturbation-assisted nanofusion technique to construct hierarchically superstructured MOFs. In particular, the mesopores in the MOF structure enabled the confinement of large dye species, resulting in fluorescent MOF materials, which can serve as a new type of ratiometric luminescent sensors for typical volatile organic compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Tailoring dye-sensitized upconversion nanoparticle excitation bands towards excitation wavelength selective imaging

One of the key roadblocks in UCNP development is its extremely limited choices of excitation wavelengths. We report a generic design to program UCNPs to possess highly tunable dye characteristic excitation bands. Using such distinctive properties, we were able to develop a new excitation wavelength selective security imaging. Finally, this work unleashed the greater freedom of the excitation wavelengths of the upconversion nanoparticles and we believe it is a game-changer in the field and this method will enable numerous applications that are currently limited by existing UCNPs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Ultrafast electrochemical preparation of graphene/CoS nanosheet counter electrodes for efficient dye-sensitized solar cells

Utilizing inexpensive, high-efficiency counter electrodes (CEs) to replace the traditional platinum counterparts in dye-sensitized solar cells (DSSCs) is worthwhile. In this paper, we detail how we synchronously prepared composite CEs of CoS nanosheet arrays and reduced graphene oxide (rGO) layers for the first time via a low temperature, ultrafast one-step electrochemical strategy. With this approach, the whole fabrication process of the composite CEs was only a small percentage of the average time (~15 hours) using other methods. The DSSC assembled with the rGO–CoS composite CE achieved an enhanced power conversion efficiency (PCE) of 8.34%, which is dramatically higher than 6.27% of pure CoS CE-based DSSC and even exceeds 7.50% of Pt CE-based DSSC. The outstanding PCE breakthrough is undoubtedly attributed to the enhancement in electrocatalytic ability of the rGO–CoS composite CE due to the incorporation of highly conducting rGO layers and the GO layers-induced growth of CoS nanosheet arrays with higher density and larger surface area. Therefore, lower charge-transfer resistance and higher exchange current density can be achieved as corroborated by the electrochemical impedance spectra (EIS) and Tafel polarization curves (TPCs). As a result, further experiments also proved that the electrochemical strategy exhibited its universality of fabricating other graphene-enhanced chalcogenide functional composite films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Silicon incorporation in polymethine dyes

Methods to red-shift fluorophores have garnered considerable interest due to the broad utility of low energy light. The incorporation of silicon into xanthene and coumarin scaffolds has resulted in an array of visible and near-infrared fluorophores. In this paper, we extend this approach to polymethine dyes, another popular fluorophore class, performing experimental and computational analyses. We found that when oxygen was replaced with SiMe 2 , bathochromic shifts of up to 121 nm and fluorophores with emission above 900 nm were achieved.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Dye-sensitized solar cells strike back

Dye-sensitized solar cells (DSCs) are celebrating their 30 th birthday and they are attracting a wealth of research efforts aimed at unleashing their full potential. Righteous font designed by Astigmatic and licensed under the Open Font License.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Synthesis and Characterization of Acridinium Dyes for Photoredox Catalysis

Photoredox catalysis is a rapidly evolving platform for synthetic methods development. The prominent use of acridinium salts as a sustainable option for photoredox catalysts has driven the development of more robust and synthetically useful versions based on this scaffold. However, more complicated syntheses, increased cost, and limited commercial availability have hindered the adoption of these catalysts by the greater synthetic community. By utilizing the direct conversion of a xanthylium salt into the corresponding acridinium as the key transformation, we present an efficient and scalable preparation of the most synthetically useful acridinium reported to date. This divergent strategy also enabled the preparation of a suite of novel acridinium dyes, allowing for a systematic investigation of substitution effects on their photophysical properties.

Chemistry↗
DOE OSTI2011

Assessment of the ΔSCF density functional theory approach for electronic excitations in organic dyes

Here, this article assesses the accuracy of the ΔSCF method for computing low-lying HOMO→LUMO transitions in organic dye molecules. For a test set of vertical excitation energies of 16 chromophores, surprisingly similar accuracy is observed for time-dependent density functional theory and for ΔSCF density functional theory. In light of this performance, we reconsider the ad hoc ΔSCF prescription and demonstrate that it formally obtains the exact stationary density within the adiabatic approximation, partially justifying its use. The relative merits and future prospects of ΔSCF for simulating individual excited states are discussed.

solar (photovoltaic), solid state lighting, photos↗
DOE OSTI2012

Theoretical study of charge recombination at the TiO{sub 2}-electrolyte interface in dye sensitised solar cells

The charge recombination reaction from the semiconductor (TiO{sub 2}) conduction band to electron accepting electrolytes (I{sub 2}, I{sub 2}{sup -}, I{sub 3}{sup -}) in dye-sensitised solar cells is investigated theoretically. The non-adiabatic theory of electron transfer has been adapted to compute the charge transfer rate measured in different experimental settings (namely with and without external illumination). In both cases we are able to provide an atomic level description of the charge recombination to the electrolyte (CRE), which is in good agreement with the experimental data available. The model employs a detailed density-functional theory (DFT) description of the semiconductor-electrolyte interface and the internal reorganization energy. A continuum dielectric model is used to evaluate the external component of the reorganization energy due to the solvent degrees of freedom. The intrinsic limitations of DFT are kept to a minimum by taking two key energetic parameters (the conduction band edge and the reaction energy) from the experiments. The proposed methodology correctly reproduces (i) the ratio between CRE rate to iodine and triiodide in dark, (ii) the absolute CRE rate to triiodide in dark, and (iii) the absolute CRE rate to I{sub 2}{sup -} under illumination.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Holographic modification of TiO{sub 2} nanostructure for enhanced charge transport in dye-sensitized solar cell

We show that the photocurrent and energy conversion efficiency of dye-sensitized solar cells can be greatly enhanced with holographic modification to the morphology of TiO{sub 2} electrode. The nanoporous electrode coated onto conducting glass was irradiated by three interfering laser beams at 1064 nm incident from the backside of the substrate. This generated two-dimensional periodic pillars of higher density in the electrode, through which the photoexcited electrons could be extracted more effectively. The cells fabricated with modified electrodes exhibited average photocurrent and efficiency of 17.14 mA/cm{sup 2} and 9.03%, while 14.91 mA/cm{sup 2} and 7.83% were obtained from the reference cells. It was attributed to the enhanced charge transport accompanied by the reduction of internal resistance of the electrode.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

UV light induced photodegradation of organic dye by ZnO nanocatalysts

Ultraviolet light induced photocatalytic activity of ZnO nanocatalyst prepared using a wet chemical precipitation route and mineralization of the methyl orange (MO) dye has been carried out in a photocatalytic reactor. The degradation of the MO was monitored spectrophotometrically and showed a decolorization efficiency of 92% after nine hours of irradiation in the MO-ZnO/UV light system. The blue shifting of maximum peak position of the MO and the formation of extra peak at 247 nm during irradiation time advances revealed that MO degrades in the form of intermediates during the photocatalytic process.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Channeling of electron transport to improve collection efficiency in mesoporous titanium dioxide dye sensitized solar cell stacks

Dye-sensitized solar cell (DSC) modules are generally made by interconnecting large photoelectrode strips with optimized thickness (∼14 μm) and show lower current density (J{sub SC}) compared with their single cells. We found out that the key to achieving higher J{sub SC} in large area devices is optimized photoelectrode volume (V{sub D}), viz., thickness and area which facilitate the electron channeling towards working electrode. By imposing constraints on electronic path in a DSC stack, we achieved >50% increased J{sub SC} and ∼60% increment in photoelectric conversion efficiency in photoelectrodes of similar V{sub D} (∼3.36 × 10{sup −4} cm{sup 3}) without using any metallic grid or a special interconnections.

30 DIRECT ENERGY CONVERSION↗