Less strained and more efficient GaN light-emitting diodes with embedded silica hollow nanospheres.

Light-emitting diodes (LEDs) become an attractive alternative to conventional light sources due to high efficiency and long lifetime. However, different material properties between GaN and sapphire cause several problems such as high defect density in GaN, serious wafer bowing, particularly in large-area wafers, and poor light extraction of GaN-based LEDs. Here, we suggest a new growth strategy for high efficiency LEDs by incorporating silica hollow nanospheres (S-HNS).

Template-free uniform-sized hollow hydrogel capsules with controlled shell permeation and optical responsiveness.

This study has established a robust and straightforward method for the fabrication of uniform poly(vinylamine) hydrogel capsules without using templates that combines the dispersion polymerization and the sequential hydrolysis/cross-linking. The particle sizes are determined by the degree of cross-linking as well as by the cross-linking reaction time, while the shell thickness is independent of these variables. Diffusion-limited reactions occur at the periphery of the particles, leading to the formation of hydrogel shells with a constant thickness.

Bright and efficient full-color colloidal quantum dot light-emitting diodes using an inverted device structure.

We report highly bright and efficient inverted structure quantum dot (QD) based light-emitting diodes (QLEDs) by using solution-processed ZnO nanoparticles as the electron injection/transport layer and by optimizing energy levels with the organic hole transport layer. We have successfully demonstrated highly bright red, green, and blue QLEDs showing maximum luminances up to 23,040, 218,800, and 2250 cd/m(2), and external quantum efficiencies of 7.3, 5.

Face selection in one-step bending of Janus nanopillars.

We introduce a one-step procedure of bending nanopillars, which simply involves oblique metal deposition at a tilted angle of 45 degrees on the pillars by thermal evaporation. The face selection in the bending procedure was determined by the nature of residual stress generated in the metal film during evaporation. If the stress was tensile as with many metals (sigma(f) > 0), the Janus nanopillars were bent toward the metal face; if the residual stress was compressive as in the case of Al (sigma(f) < 0), they were bent toward the polymer face.

Characterization of quantum dot/conducting polymer hybrid films and their application to light-emitting diodes.

Quantum dot/conducting polymer hybrid films are used to prepare light-emitting diodes (LEDs). The hybrid films (CdSe@ZnS quantum dots excellently dispersed in a conducting polymer matrix, see figure) are readily prepared by various solution-based processes and are also easily micropatterned. The LEDs exhibit a turn-on voltage of 4 V, an external quantum efficiency greater than 1.

Polymerizable Well-Defined Oligo(thiophene amide)s and their ROMP Block Copolymers.

We report the synthesis of conjugated thiophene amide oligomers that constitute a new class of chromophores with potential for optoelectronic applications. The synthesis of defined norbornene-substituted oligothiophene amides using conventional coupling chemistry is described. Their electronic properties depend on the degree of oligomerization as UV/Vis and fluorescence spectroscopy demonstrate.