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.     

Plasmon‐Resonance‐Based Generation of Cathodic Photocurrent at Electrodeposited Gold Nanoparticles Coated with TiO2 Films

Reversed photoresponse: Indium tin oxide (ITO)/Au nanoparticle (NP)/TiO₂ electrodes (see picture) exhibit cathodic photocurrents and positive photopotentials under visible light, whereas ITO/TiO₂/Au NP electrodes show an inverted response. This behavior indicates that electron transfer occurs from the plasmon‐excited Au NPs to the TiO₂ film. An enhanced O₂ photoreduction activity is found for ITO/Au NP/TiO₂/Pt electrodes.

     

Luminescence and long-lasting afterglow in Mn<Superscript>2+</Superscript> and Eu<Superscript>3+</Superscript> co-doped ZnO–GeO<Subscript>2</Subscript> glasses and glass ceramics prepared by sol–gel method

To develop new fluorescent and afterglow materials, Mn²⁺ and Eu³⁺ co-doped ZnO–GeO₂ glasses and glass ceramics were prepared by a sol–gel method and their optical properties were investigated by measuring luminescence, excitation and afterglow spectra, and luminescence quantum yield (QY). Under UV irradiation at 254 nm, some glasses and all of the glass ceramics showed green luminescence peaking at 534 nm due to the ⁴T₁ → ⁶A₁ transition of tetrahedrally coordinated Mn²⁺ ions. The strongest luminescence was observed in a glass ceramic of 0.1MnO–0.3Eu₂O₃–25ZnO–75GeO₂ heat treated at 900 °C, with QY of 49.8%. All of the green-luminescent glasses and glass ceramics showed green afterglow, and the afterglow lasting for more than 60 min was obtained in a glass ceramic heat treated at 900 °C. It is considered that the Eu³⁺ ions may behave as electron trapping centers to be associated with the occurrence of the green afterglow due to the Mn²⁺ ions in the co-doped system.     

Enhancement in fluorescence response by a quencher for amiloride upon binding to thymine opposite an abasic site in a DNA duplex

By using iodide (I⁻) as a quencher, we successfully improve the fluorescence response of amiloride when binding to thymine opposite an AP site in a 21-meric DNA duplex. From fluorescence measurements, as compared to the NaCl solutions, the addition of NaI as a quencher as well as salt to adjust the ionic strength effectively suppresses the background fluorescence from unbound amiloride in a solution. The Stern-Volmer analysis shows that the bound amiloride to the nucleobase at the AP site is unexposed to NaI quencher. Therefore the high signal-to-background fluorescence response of amiloride is obtained. Such enhancement in fluorescence response of amiloride by using the quencher can provide the significant improvement of the detection limit for DNA duplexes carrying T target base. The method presented in this study is simple and effective. The present method could be applicable to other detection system where microenvironment of fluorophores changes at a recognition event.     

Preparation of Ni nanoparticles between montmorillonite layers utilizing dimethylaminoborane as reducing agent

Preparation of Ni nanoparticles between montmorillonite layers using dimethylaminoborane (DMAB) as a reducing agent is reported. The DMAB molecules are first intercalated into the interlayer space of Ni-montmorillonite (Ni-mont). Then, as a result of a heating process, the DMAB is decomposed to release electrons for the reduction of the Ni ions. From high-resolution TEM images, it is demonstrated that the deposited Ni nanoparticles with about 1-2 nm in size are formed uniformly over the entire area of the Ni-mont matrix. Considering the gallery height calculated by subtracting the silicate sheet thickness from the basal spacing (1.30 nm), the morphology of the formed Ni nanoparticles in the interlayer space is thought to be disc-like in shape with a thickness of 0.3-0.4 nm and an average lateral size of 1.2 nm.     

Fusion of photochromic reaction and synthetic reaction: photoassisted cyclization to highly strained chiral azobenzenophanes

A method for synthesizing highly strained cyclic structures by combining photochromic and synthetic reactions is described. Tightly linked azobenzene-binaphthyl dyads (R)-4 and (R)-6 could not be obtained by conventional cyclization, but continuous application of photoirradiation, which induced (E)→(Z) isomerization of the azobenzene moiety, allowed the cyclization reaction to proceed, affording the desired chiral azobenzenophanes.