New method to measure whole-wavelength transmittance of TCO substrates for thin-film silicon solar cells

High transmittance of transparent conductive oxide (TCO) substrates is one of the most important factors for achieving high efficiency in thin-film silicon solar cells. Immersion (IM) method with CH₂I₂ liquid is widely used for the evaluation of optical properties (transmittance, reflectance and absorption) for TCO substrates with textured surface in order to reduce the scattering at the TCO surface. However, in order to measure transmittance accurately, three problems have been found. (1) CH₂I₂ liquid itself absorbs the light in short wavelength region. (2) The transmittance around the absorption edge of CH₂I₂ liquids is very sensitive to its amount. (3) Scattering cannot be suppressed when the scattering surfaces are more than 2 surfaces (for example, TCO on reactive ion etching (RIE) processed glass). To overcome these problems, we proposed a new setup to measure optical properties of TCO substrates by holding the samples inside the integral sphere. As the results, we have confirmed that their absorption in all wavelength could be measured accurately and the transmittance measured by the new method was well consistent with the external quantum efficiency (EQE) of the fabricated cell while the transmittance measured with conventional IM method showed differently. Therefore, this new method could be a useful tool to evaluate TCO substrates for thin-film silicon solar cells.     

"ON-OFF" switching of europium complex luminescence coupled with a ligand redox process

A triarylamine-functionalized terpyridine ligand formed a highly coordinated complex with europium tris(β-diketonate), which displayed reversible 'ON-OFF' luminescence switching coupled with a ligand redox process of triarylamine/triarylaminium cations.     

Real-time propagation time-dependent density functional theory study on the ring-opening transformation of the photoexcited crystalline benzene

Mechanism of the ring-opening transformation in the photoexcited crystalline benzene is investigated on the femtosecond scale by a computational method based on the real-time propagation (RTP) time-dependent density functional theory (TDDFT). The excited-state dynamics of the benzene molecule is also examined not only for the distinction between the intrinsic properties of molecule and the intermolecular interaction but for the first validation using the vibration frequencies for the RTP-TDDFT approach. It is found that the vibration frequencies of the excited and ground states in the molecule are well reproduced. This demonstrates that the present method of time evolution using the Suzuki-Trotter-type split operator technique starting with the Franck-Condon state approximated by the occupation change of the Kohn-Sham orbitals is adequately accurate. For the crystalline benzene, we carried out the RTP-TDDFT simulations for two typical pressures. At both pressures, large swing of the C-H bonds and subsequent twist of the carbon ring occurs, leading to tetrahedral (sp3-like) C-H bonding. The nu4 and nu16 out-of-plane vibration modes of the benzene molecule are found mostly responsible for these motions, which is different from the mechanism proposed for the thermal ring-opening transformation occurring at higher pressure. Comparing the results between different pressures, we conclude that a certain increase of the intermolecular interaction is necessary to make seeds of the ring opening (e.g., radical site formation and breaking of the molecular character) even with the photoexcitation, while the hydrogen migration to fix them requires more free volume, which is consistent with the experimental observation that the transformation substantially proceeds on the decompression.     

Oxidative dehydrogenation of ethane over Cr/ZSM-5 catalysts using CO2 as an oxidant

Highly active catalysts for oxidative dehydrogenation of ethane with CO2 were characterized by temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), Fourier transform infrared (FTIR) spectroscopy, and X-ray absorption fine-structure (XAFS) analysis. In the active catalysts, Cr/H-ZSM-5 (SiO2/Al2O3 > 190), Cr6+ = O, or possibly Cr5+ = O was the catalytic species on the zeolite support. In contrast, little Cr6+ (or Cr5+) was detected in the less-active catalysts. The Cr6+ (or Cr5+) species was reduced to an octahedral Cr3+ species by treatment with ethane at 773 K, and the reduced Cr species was reoxidized to the Cr6+ (or Cr5+) species by treatment with CO2 at 673-773 K. The Cr redox cycle played an important role in the catalyst's high activity.     

Novel and efficient synthesis of cyanidin 3-O-beta-D-glucoside from (+)-catechin via a flav-3-en-3-ol as a key intermediate

[reaction: see text] A novel and efficient synthesis of cyanidin 3-O-beta-D-glucoside (1) was accomplished the first time by a biomimetic oxidation route. From (+)-catechin, 3-OH was glucosylated, and the 4-position of the nucleus was then oxidized and dehydrated to give the 5,7,3',4'-tetra-O-(tert-butyldimethylsilyl)flav-3-en-3-ol 3-O-glucoside (8) as a key intermediate. 8 was deprotected and oxidized under air in hydrogen chloride-MeOH to give 1.     

STM studies on the reconstruction of the Ni2P (101̅0) surface

The surface structure of Ni₂P (101?0), a model for highly active hydrodesulfurization catalysts, was studied using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) in order to understand the reconstruction of the surface layers. Annealing at 573 K revealed a (1 × 1) LEED pattern which changed to a c(2 × 4) arrangement by further heating to 723 K. Atomic scale STM images were obtained for both the (1 × 1) and c(2 × 4) structures. Bright spots observed in the STM images were interpreted to be due to surface phosphorus atoms and this was supported by a density functional theory (DFT) simulation. Several possible models for the c(2 × 4) reconstructed structures were proposed including a P-dimer defect model, a missing-row model and a missing-row + added-row model. The last model gave the best explanation for the c(2 × 4)structure. The mechanism for the c(2 × 4) reconstruction on the Ni₂P (101?0) surface is discussed.     

GaP Raman Terahertz high accuracy spectrometer and its application to detect organic and inorganic crystalline defects

One of the most important uses of THz spectrometry is to detect defects in molecular structure or in crystals efficiently. We applied GaP Raman THz (GRT) spectrometer to detect and evaluate defects in inorganic and organic materials. High THz-wave absorption due to high defect density of GaSe crystal lowered the efficiency of THz wave generation, when the crystal is used as nonlinear material for DFG (Difference Frequency Generation). Defects in organic molecules could be observed as changes in frequency, intensities of the absorption, and broadenings of the spectra.     

Practical synthesis of adenosine 3′,5′-cyclic monophosphorodithioate

Adenosine 3′,5′-cyclic monophosphorodithioate (cAMPS₂), which has two exocyclic sulfurs directly attached to phosphorus, was synthesized from adenosine phosphoramidite by intramolecular cyclization employing the phosphotriester method as a key step.     

Electrochemical and Electrochromic Properties of Polymer Complex Films Composed of Polytetramethyleneviologen and Poly-[p-Styrenesulfonic Acid] Containing a Conductive Powder

The electrochemical and electrochromic properties of polymer films containing a conductive powder (SnO₂/TiO₂) have been investigated. The films are complexes of polytetramethyleneviologen and poly(p-styrenesulfonic acid). It was found that the coloration (purple) and bleaching rates of the composite films increase markedly with increasing conductive powder content(x). The coloring and bleaching of the composite film with x = 95 wt% were about 7 and 44 times faster, respectively, than those for an equivalent film without conductive powder. This increase in the rate of color change by introduction of a conductive powder was found to be correlated with the apparent diffusion coefficient (D _app) for the diffusionlike charge-transport process within the composite films which increases with increasing x. The D _app for the reduction process of the film with x = 95 wt% was larger by about 3 orders of magnitude than that for the unfilled film.