Effect of nano-silica filler on the uniform packaging of white light emitting diodes.

The packaging process of white light-emitting diodes (WLEDs) take a relatively long time, even when utilizing an automated dispensing system. Therefore the silicone-based packaging formulation and control of rheology during the packaging of LEDs are very important. The effect of phosphor settling during the curing state of LED packaging has been reported. In this work we studied the effect of phosphor paste on the dispensing stage of the WLEDs packaging process utilizing nanosilica particles as viscosity modifiers. With nano-silica in the silicone resin the sedimentation of YAG phosphor particles were effectively blocked and a uniform distribution of YAG phosphor in the cured silicon resin could be achieved. We also examined the incorporation of red quantum dots (QDs) to improve the color rendering index of the WLEDs with the aid of nano-silica as a rheological additive. The application of nano-silica in the layer-by-layer type encapsulation of red QDs was found to be effective in WLEDs packaging, which improved the color rendering index with warm white emission.

Highly luminescent InP/GaP/ZnS nanocrystals and their application to white light-emitting diodes.

Highly stable and luminescent InP/GaP/ZnS QDs with a maximum quantum yield of 85% were synthesized by in situ method. The GaP shell rendered passivation of the surface and removed the traps. TCSPC data showed an evidence for the GaP shell. InP/GaP/ZnS QDs show better stability than InP/ZnS. We studied the optical properties of white QD-LEDs corresponding to various QD concentrations. Among various concentrations, the white QD-LEDs with 0.5 mL of QDs exhibited a luminous efficiency of 54.71 lm/W, Ra of 80.56, and CCT of 7864 K.

Spray coating of carbon nanotube on polyethylene terephthalate film for touch panel application.

From a technical perspective, the major limiting factors for the wide adoption of CNT films are the DC conductivity, uniformity of sheet resistance and good adhesion of CNT on film substrate. In this study, the effects of sonificator and process time on the zeta potential and sheet resistance of the CNT-PET film show that although the dispersing power of horn-type sonificator is stronger than that of bath-type, the SWCNT solution obtained with horn-type sonificator agglomerates faster. Likewise, it has been noted that the SWCNT solutions with low enough zeta potentials exhibit higher sheet resistance after making CNT-PET films due to the damage to SWCNTs caused by high dispersion force. Since the spray coating of SWCNT solution gives the SWCNT-SDS composite layer on PET film after drying, the excess SDS should be washed off. The removal of excess SDS was conducted by dipping in the 3 N HNO3 and SOCl2 solution and washing with deionized water followed by heat treatment in a 120 degrees C convection oven for 30 min. The lift-off of SWCNT-SDS composite layer after 40 min dipping in the 3 N HNO3 solution appeared to be due to the continued permeation leading to swelling of the SDS layer by the 3 N HNO3 aqueous solution. It was found that ten times of spray coating cycle gave CNT-PET film the sheet resistance of 310 Ω/[square] and transmittance of 81%. The TSP made with CNT-PET film exhibited a performance equal to the one made with ITO-PET film.

High performance of GaN-based flip-chip light-emitting diodes with hole-shape patterned ITO ohmic contact layer and AgIn reflector.

The enhancement of light extraction efficiency is observed when the hole-shape patterned ITO ohmic contact layer and AgIn reflector is adopted in GaN-based flip-chip (FC) light emitting diodes (LEDs). ITO layer (140 nm) and AgIn (200 nm) was deposited on the top of p-GaN by in-line DC sputtering and electron beam evaporating system, respectively. The ITO ohmic contact layer showed a low specific contact resistance of 2.66 x 10(-5) Omega cm(-2) and high transmittance of >85% at visible spectral regions. The AgIn reflector exhibited a low specific contact resistance of 1.90 x 10(-5) Omega cm(-2) and high reflectance of approximately 84% at visible spectral regions. Comparing with unpatterned ITO/AgIn layer, the optical output power of GaN-based FC LEDs improves approximately 30% by the adoption of micro size hole-shape patterned ITO ohmic contact layer and AgIn reflector.

In vitro anti-bacterial and cytotoxic properties of silver-containing poly(L-lactide-co-glycolide) nanofibrous scaffolds.

Electrospinning has recently emerged as a leading technique for the formation of nanofibrous structures made of organic and inorganic components. In this study, nanofibrous scaffolds were prepared by electrospining a bend solution of poly(L-lactide-co-glycolide) (PLGA) and silver nanoparticles in 1,1,1,3,3,3,-hexafluoro-2-propanol (HFIP). The resulting fibers ranged from 420 to 590 nm in diameter. To evaluate the possibility of using silver-containing PLGA as a tissue engineering scaffold, experiments on cell viability and antibacterial activity were carried out. As a result, PLGA nanofibrous scaffolds having silver nanoparticles of more than 0.5 wt% showed antibacterial effect against Staphylococcus aureus and Klebsiella pneumonia. Furthermore, silver-containing PLGA nanofibrous scaffolds showed viability, indicating their possible application in the field of tissue engineering.

Effect of hole injection layer/hole transport layer polymer and device structure on the properties of white OLED.

Copolymers containing carbazole and aromatic amine unit were synthesized by using Pd-catalyzed polycondensation reaction. The polymers were characterized in terms of their molecular weight and thermal stability and their UV and PL properties in solution and film state. The band gap energy of the polymers was also determined by the UV absorption and HOMO energy level data. The polymers had high HOMO energy level of 5.19-5.25 eV and work function close to that of ITO. The polymers were thus tested as hole injection/transport layer in the white organic light emitting diodes (OLED) by using 4,4'-bis(2,2-diphenyl-ethen-1-yl)diphenyl (DPVBi) as blue emitting material and 5,6,11,12-tetraphenylnaphthacene (Rubrene) as orange emitting dopant. The synthesized polymer, poly bis[6-bromo-N-(2-ethylhexyl)-carbazole-3-yl] was found to be useful as hole injection layer/hole transport layer (HIL/HTL) multifunctional material with high luminance efficiency and stable white color coordinate in the wide range of applied voltage.

Highly efficient and low voltage silver nanowire-based OLEDs employing a n-type hole injection layer.

Highly flexible and efficient silver nanowire-based organic light-emitting diodes (OLEDs) have been successfully fabricated by employing a n-type hole injection layer (HIL). The silver nanowire-based OLEDs without light outcoupling structures exhibited excellent device characteristics such as extremely low turn-on voltage (3.6 V) and high current and power efficiencies (44.5 cd A(-1) and 35.8 lm W(-1)). In addition, flexible OLEDs with the silver nanowire transparent conducting electrode (TCE) and n-type HIL fabricated on plastic substrates showed remarkable mechanical flexibility as well as device performance.

Exciton coupling effects and conformational change of perhexyloligosilanes with optically active methyl(1-naphthyl)phenylsilyl terminals.

Perhexyloligosilanes (R,R)-(+)-MeNpPhSi*(Hex(2)Si)(n)Si*PhNpMe (n = 2; (R,R)-(+)-4a, n = 4; (R,R)-(+)-6a, n = 6; (R,R)-(+)-8a) with chiral methyl(1-naphthyl)phenylsilyl terminals were synthesized and characterized. The absorption wavelengths lambda(max) by (1)L(a,Ph) transition of phenyl chromophore conjugated with oligosilane units in (R,R)-(+)-4a - (R,R)-(+)-8a show bathochromic shift of about 3-4 nm compared with those of the alpha,omega-phenyl substituted perhexyloligosilanes Ph(Hex(2)Si)(m)Ph (m = 4; 4b, m = 6; 6b, m = 8; 8b) having the same silicon chain length. Longer chain length induces the separated lambda(max) of (1)L(a,Ph) from (1)B(b,Np) of naphthyl chromophore with positive exciton chiralities. In (R,R)-(+)-8a, although the extremum wavelengths lambda(ext) of exciton coupling between (1)B(b,Np) and (1)L(a,Ph) are separated by about 80 nm, the compound retains the positive exciton chirality, which provides definite information on the absolute configuration of terminal chiral silicon atoms. Bulky terminal substituents and lowering the temperature affect the conformation of the main chain, inducing extended silicon backbone structure.