A new solution processable nanocomposite material has been prepared via the Heck coupling of octavinylsilsesquioxane with a selected bromoaromatic hole transport compound. Resultant electroluminescent devices show an 18% improvement in external quantum efficiencies over their small molecule analogues.

The synthesis and characterization of octavinylsilsesquioxane (OVS)-based nanocomposite dendrimers with luminescent and charge transport properties are reported. The nanocomposite dendrimers were prepared in high yield using mild Heck chemistry of mono-haloaromatic compounds with the peripheral vinylsilane groups of OVS. Attachment of 2-naphthalene, 2-(9,9-dimethyl)fluorene, and 2-(4-phenyl)-5-(1-naphthyl)-1,3,4-oxadiazole resulted in materials with blue-violet emission (360-380 nm) and photo-luminescent quantum efficiencies (PLQEs) from 1 to 26%. Blue-green emission was observed for attachment of 1-pyrene, 9-anthracene, and N1-(4-phenyl)-N1,N4,N4-triphenylbenzene-1,4-diamine with PLQEs ranging from 23 to 50%. Despite the planar characteristics of the organic dendrons, the nanocomposite dendrimers are completely amorphous and have high glass transition temperatures (Tg) ranging from 115 to 186 degrees C with decomposition temperatures (Td) exceeding 450 degrees C. Matrix-assisted laser desorption ionization-time of flight shows that unlike traditional Heck chemistry, haloaromatic compounds are adding twice across the vinylsilane groups. Finally, organic light emitting diodes using the aromatic amine-based dendrimer as hole injection layers show 55% improvement in device efficiency over traditional materials (5.16 vs. 3.24 cd A(-1)) with brightness levels exceeding 40,000 cd m(-2).

We discuss the sensitivity enhancement of bottom-gate type amorphous InGaZnO 4 thin-film transistor (a-InGaZnO TFT) pH sensors from the viewpoint of top-gate effects. Comparing the top-gate effects in a-InGaZnO TFTs having TaO x and SiO x ion-sensitive insulators, we draw an analogy between the operations of dual-gate TFTs and TFT pH sensors. Our new concept for enhancing pH sensitivity is characterized by a high capacitance ratio of the ion-sensitive insulator to the bottom-gate insulator and pH sensing utilizing threshold-voltage shifts in bottom-gate transfer characteristics. The close similarity between top-gate effects and pH sensitivity strongly suggests that a common mechanism underlies the phenomena. We discuss the mechanism on the basis of the material properties of a-InGaZnO and the silicon-on-insulator (SOI) model that relates bottom-and top-gate electric fields in fully depleted operations. We believe that the pH-sensitivity enhancement utilizing top-gate effects is one of the potential applications that would make the most of the intrinsic features of a-InGaZnO TFTs.

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