A5084025265- TiO2 Photocatalysis and Solar Cells
- Advanced Photocatalysis Techniques
- Photochemistry and Electron Transfer Studies
- Spectroscopy and Quantum Chemical Studies
- Electrochemical Analysis and Applications
- Quantum Dots Synthesis And Properties
- Organic Electronics and Photovoltaics
- Perovskite Materials and Applications
- Luminescence and Fluorescent Materials
- Conducting polymers and applications
- Organic Light-Emitting Diodes Research
- Analytical Chemistry and Sensors
- Photoreceptor and optogenetics research
- Advanced Nanomaterials in Catalysis
- Ionic liquids properties and applications
- Chalcogenide Semiconductor Thin Films
- Luminescence Properties of Advanced Materials
- Copper-based nanomaterials and applications
- Gold and Silver Nanoparticles Synthesis and Applications
- Gas Sensing Nanomaterials and Sensors
- Electronic and Structural Properties of Oxides
- Laser-Ablation Synthesis of Nanoparticles
- Crystallization and Solubility Studies
- ZnO doping and properties
- X-ray Diffraction in Crystallography
Nihon University
2016-2025
Applied Science Private University
2025
Koriyama Institute of Health Sciences
2015-2020
National Institute of Advanced Industrial Science and Technology
2005-2016
National Institute for Materials Science
1996-2010
University of Tsukuba
2009-2010
Hamamatsu Photonics (Japan)
2009
MacDiarmid Institute for Advanced Materials and Nanotechnology
2009
Shinshu University
2009
University of Otago
2009
We have developed novel coumarin dyes for use in dye-sensitized nanocrystalline TiO2 solar cells (DSSCs). The absorption spectra of these are red-shifted remarkably the visible region relative to spectrum C343, a conventional dye. Introduction methine unit (−CHCH−) connecting both cyano (−CN) and carboxyl (−COOH) groups into framework expanded π conjugation dye thus resulted wide region. These performed as efficient photosensitizers DSSCs. monochromatic incident photon-to-current conversion...
By using femtosecond transient absorption spectroscopy with visible pump and IR probe to observe generation of injected electrons, we could directly plasmon-induced electron transfer from 10 nm gold nanodots TiO2 nanocrystalline film. It was revealed that the reaction time within 240 fs yield about 40%.
We have developed oligothiophene-containing coumarin dyes fully functionalized for dye-sensitized nanocrystalline TiO2 solar cells (DSSCs). DSSCs based on the gave good performance in terms of incident photon-to-current conversion efficiency (IPCE) range 400−800 nm. A energy-to-electricity (η) 7.4% was obtained with a DSSC 2-cyano-3-[5'-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)-[2,2']bithiophenyl-5-yl]acrylic acid (NKX-2677) under...
The efficiency of electron injection from excited N3 dye (cis-bis-(4,4'-dicarboxy-2,2'-bipyridine) dithiocyanato ruthenium(II), Ru(dcbpy)2 (NCS)2), into various nanocrystalline semiconductor (ZrO2, TiO2, ZnO, Nb2O5, SnO2, In2O3) films was studied by transient absorption spectroscopy. For or In2O3 films, efficiencies were found to be very high; for ZrO2 film, the low. These findings indicate that occurs efficiently if LUMO level is located sufficiently far above bottom conduction band film....
Reactive species, holes, and electrons in photoexcited nanocrystalline TiO2 films were studied by transient absorption spectroscopy the wavelength range from 400 to 2500 nm. The electron spectrum was obtained through a hole-scavenging reaction under steady-state light irradiation. can be analyzed superposition of free-electron trapped-electron spectra. By subtracting spectrum, trapped holes obtained. As result, three reactive speciestrapped free electronswere identified spectrum. reactivity...
Abstract Novel conjugated organic dyes that have N , ‐dimethylaniline (DMA) moieties as the electron donor and a cyanoacetic acid (CAA) moiety acceptor were developed for use in dye‐sensitized nanocrystalline‐TiO 2 solar cells (DSSCs). We attained maximum solar‐energy‐to‐electricity conversion efficiency (η) of 6.8 % under AM 1.5 irradiation (100 mW cm –2 ) with DSSC based on 2‐cyano‐7,7‐bis(4‐dimethylamino‐phenyl)hepta‐2,4,6‐trienoic (NKX‐2569): short‐circuit photocurrent density ( J sc =...
Porphyrin molecules offer immense potential as the light harvesting component of dye-sensitised nanocrystalline TiO2 solar cells. Synthetic porphyrin dyes were amongst first trialled for sensitisation inorganic semiconducting oxides. Today, they exhibit best performance reported Accompanying significant improvement over last two decades is a much improved understanding efficiency-determining fundamental electron transfer steps, from charge photogeneration to recombination. In this feature...
To investigate the primary process of photocatalytic oxidation TiO2, interfacial charge-transfer reaction trapped holes formed in nanocrystalline TiO2 films by UV irradiation was directly measured highly sensitive femtosecond and nanosecond transient absorption spectroscopy under low intensity excitation condition to avoid fast electron−hole recombination. Accordingly, rates yields several alcohols adsorbed on were evaluated successfully.
The transient absorption of nanocrystalline TiO(2) films in the visible and IR wavelength regions was measured under weak-excitation condition, where second-order electron-hole recombination process can be ignored. intrinsic dynamics pairs femtosecond to picosecond time range elucidated. Surface-trapped electrons surface-trapped holes were generated within approximately 200 fs (time resolution). electrons, which gave an peak at around 800 nm, bulk absorbed region, decayed with a 500-ps...
To study plasmon-induced charge-transfer mechanisms between excited gold nanoparticles and TiO2, ultrafast visible-pump/infrared-probe femtosecond transient absorption spectroscopy was used charge separation recombination dynamics in gold−TiO2 nanoparticle systems were explored. TiO2 of different diameters (9, 20, 30, 50 nm) chosen as electron acceptors for with a 10 nm diameter. Electron transfer from to the conduction band observed by electrons at 3440 after optical excitation surface...
Poly(3-hexylthiophene) (P3HT) [90–93% regioregular, Mw ∼55 kDa, PDI <2] is studied by transient absorption spectroscopy and the properties of excited state P3HT in solution thin film contrasted. In solution, excitation yields first singlet which has a characteristic lifetime ∼600 ps, measured high quantum yield fluorescence chlorobenzene 0.33 ± 0.07. The long lived (∼μs) species ascribed to triplet state, formed intersystem crossing from with around 300 ns aerated solution. By contrast solid...
We measured the fluorescence quantum yield (Φf) of several aromatic hydrocarbon crystals: p-terphenyl, trans-stilbene, anthracene, pyrene, and α-perylene. The Φf is reduced by chemical impurities, structural defects, reabsorption fluorescence. To minimize effect impurities we evaluated highly purified single crystals. also powder samples prepared mechanical milling crystals to assess defects induced milling. estimated lower limit values be 0.80 for >0.65 >0.64 0.68 0.31
A series of platinum-based sensitizers the general type Pt(NN)(SS), where NN is 4,4'-dicarboxy-2,2'-bipyridine (dcbpy) or 4,7-dicarboxy-1,10-phenanthroline (dcphen) and SS ethyl-2-cyano-3,3-dimercaptoacrylate (ecda), quinoxaline-2,3-dithiolate (qdt), 1,2-benzenedithiolate (bdt), 3,4-toluenedithiolate (tdt), that have various ground-state oxidation potentials has been synthesized anchored to nanocrystalline titanium dioxide electrodes for light-to-electricity conversion in regenerative...
Dye-sensitized solar cells based on cis-bis-(4,4'-dicarboxy-2,2'-bipyridine) dithiocyanato ruthenium (II) (Ru(dcbpy)2(NCS)2, N3) adsorbed nanocrystalline ZnO films are a promising system as highly efficient cells. However, the performance of decreases with increasing concentration N3 dye surface films, suggesting formation aggregates. We have studied efficiency electron injection at two concentrations through fluorescence and transient absorption measurements. From measurements, we confirmed...
The transient absorption of nanocrystalline TiO2 films in the visible-to-IR wavelength region was measured under UV excitation at 266 nm order to purposely generate plural electron−hole pairs single nanoparticles. Trapped holes, trapped electrons, and bulk electrons were observed as our previous studies, where density reduction be low second-order recombination did not occur, namely, number electron hole less than unity per nanoparticle. kinetics recombination, induced a controlled manner,...
Zn−Zn porphyrin dimers have been incorporated into thin dye-sensitized solar cells (DSSCs) to boost their light harvesting efficiency. The photoexcited show efficient and fast electron injection TiO2 indicating that both chromophores contribute current generation. improved ability coupled enhanced DSSC performance demonstrates the potential of 3-D arrays as next generation harvesters for artificial energy conversion systems.
Abstract Mobilities and lifetimes of photogenerated charge carriers are core properties photovoltaic materials can both be characterized by contactless terahertz or microwave measurements. Here, the expertise from fifteen laboratories is combined to quantitatively model current‐voltage characteristics a solar cell such To this end, impact measurement conditions, alternate interpretations, experimental inter‐laboratory variations discussed using (Cs,FA,MA)Pb(I,Br) 3 halide perovskite...
Abstract With near unity quantum efficiency and operational stability surpassing 250 days in outdoor conditions, aluminum‐doped SrTiO 3 (Al:SrTiO ) with tailored cocatalysts is one of the promising photocatalysts for scalable solar H 2 production. Nevertheless, mechanistic insights behind Al‐doping Rh cocatalyst‐induced enhanced overall water splitting (OWS) are not well elucidated. Herein, detailed charge carrier dynamics from sub‐picosecond to milliseconds unveiled Al:SrTiO by transient...
Phenylethylammnonium bis(trifluoromethylsulfonyl)imide allows spontaneous perovskite passivation via hole transport material deposition for efficient and thermally stable PTAA-based solar cells.
Near-IR absorption spectra of electrons injected from excited sensitizer dyes to nanocrystalline ZnO films have been studied. The steeply increases with increasing wavelength and can be assigned the optical transition conducting higher energy levels conduction band. From measurements in various dyes, relative efficiencies electron injection obtained as a function free change (ΔG) for process. Around ΔG = 0 eV, increase gradually −ΔG they are constant at negative ΔG. We succeeded explaining...