All-solution-processed Si films with broadband and omnidirectional light absorption.

Silicon photonic structures have attracted a great deal of attention due to their potential benefits of efficient light management in optoelectronic applications. In this paper, we demonstrate broadband optical absorption enhancement in solution-processed amorphous silicon (a-Si) by leveraging the advantages of silicon photonic structures. Graded refractive index silicon multi-layer structures are employed by modulating optical constants with simple process optimization, resulting in significantly improved reflectance over a broad range of visible wavelengths. In addition, nanopatterning flexibility of solution-processed silicon provides benefits for tailoring silicon optical properties. With the incorporation of the two-dimensional submicron pattern into silicon films, the absorptivity of silicon films improves considerably below the wavelength of the bandgap (λ âˆ¼ 800 nm), and the limited bandwidth of absorptivity in silicon films can be extended to near-infrared wavelengths by coating with a thin gold layer. The methodology is generally applicable to a platform for improving the broadband optical absorption of photonic and optoelectronic devices.

Simultaneous enhancement of upconversion and downshifting luminescence via plasmonic structure.

We describe a metal nanodisk-insulator-metal (MIM) structure that enhances lanthanide-based upconversion (UC) and downshifting (DS) simultaneously. The structure was fabricated using a nanotransfer printing method that facilitates large-area applications of nanostructures for optoelectronic devices. The proposed MIM structure is a promising way to harness the entire solar spectrum by converting both ultraviolet and near-infrared to visible light concurrently through resonant-mode excitation. The overall photoluminescence enhancements of the UC and DS were 174- and 29-fold, respectively.

Reactivity of an aryl-substituted silicon-silicon triple bond: reactions of a 1,2-diaryldisilyne with alkenes.

The reactivity of a bulky, diaryl-substituted disilyne, Ar-Si identical withSi-Ar, was examined for the first time. Reaction of the disilyne with ethylene yielded an ethylene-bridged bis(silacyclopropane), which is interpreted as a further reaction product of the initially formed 1,2-disilacyclobutene species with ethylene. A cyclohexane fused with a 1,2-disilacyclobutene was obtained in the reaction with cyclohexene. In the reaction with 2,3-dimethyl-1,3-butadiene, a tricyclo derivative was isolated from the complex product mixture.

Bright Blue, Green, and Red Luminescence from Dye-Sensitized Core@Shell Upconversion Nanophosphors under 800 nm Near-Infrared Light.

In this study, Li-based blue- and green-emitting core@shell (C@S) upconversion nanophosphors (UCNPs) and NaGdF4-based red-emitting C@S UCNPs were synthesized, and IR-808 dyes were conjugated with the C@S UCNPs to enhance upconversion (UC) luminescence. The surface of the as-synthesized C@S UCNPs, which was originally capped with oleic acid, was modified with BF4- to conjugate the IR-808 dye having a carboxyl functional group to the surface of the UCNPs. After the conjugation with IR-808 dyes, absorbance of the UCNPs was significantly increased. As a result, dye-sensitized blue (B)-, green (G)-, and red (R)-emitting UCNPs exhibited 87-fold, 10.8-fold, and 110-fold enhanced UC luminescence compared with B-, G-, and R-emitting Nd3+-doped C@S UCNPs under 800 nm near-infrared (NIR) light excitation, respectively. Consequently, dye-sensitized UCNPs exhibiting strong UC luminescence under 800 nm NIR light excitation have high applicability in a variety of biological applications.

Reactivity of an aryl-substituted silicon-silicon triple bond: 1,2-disilabenzenes from the reactions of a 1,2-diaryldisilyne with alkynes.

The reactivity of a diaryl-substituted disilyne, Ar-Si[triple bond, length as m-dash]Si-Ar, with alkynes was examined. Reaction of the disilyne with acetylene yielded a 1,2-disilabenzene as the sole product.