Highly-tolerant distributed Bragg reflectors (DBRs) based on the same materials consisting of nanoporous/dense titanium dioxide (TiO2) film pair structures with wide-angle and broadband highly-reflective properties at visible wavelengths are reported. For a high refractive index contrast, the two dense and nanoporous TiO2 film stacks are alternatingly deposited on silicon (Si) substrates by a oblique angle deposition (OAD) method at two vapor flux angles (θα) of 0 and 80° for high and low refractive indices, respectively. For the TiO2 DBRs at a center wavelength (λ(c)) of 540 nm, the maximum level in reflectance (R) band is increased with increasing the number of pairs, exhibiting high R values of > 90% for 5 pairs, and the normalized stop bandwidth (∆λ/λ(c)) of ~17.8% is obtained. At λ(c) = 540 nm, the patterned TiO2 DBR with 5 pairs shows an uniform relative reflectivity over a whole surface of 3 inch-sized Si wafer and a large-scalable fabrication capability with any features. The angle-dependent reflectance characteristics of TiO2 DBR at λ(c) = 540 nm are also studied at incident angles (θ(inc)) of 20-70° for p-, s-, and non-polarized lights in the wavelength region of 350-750 nm, yielding high R values of > 70.4% at θ(inc) values of 20-70° for non-polarized light. By adjusting the λ(c)/4 thicknesses of nanoporous and dense films, for λ(c) = 450, 540, and 680 nm, tunable broadband TiO2 DBRs with high R values of > 90% at wavelengths of 400-800 nm are realized.

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Color-tunable CaWO4:xDy3+ phosphors were prepared via a simple conventional solid-state reaction and their luminescent properties were investigated as a function of Dy3+ ion concentration under 258 and 353 nm excitations. A gradual enhancement in the emission intensity was observed with the increment of Dy3+ ion concentration, reaching its maximum value when x = 0.05. The main reason for the concentration quenching of Dy3+ emission in CaWO4 host lattice is due to the electric dipole-dipole interaction. The cathodoluminescence spectra, which were measured at different accelerating voltages and filament currents, were in consistent with the photoluminescence spectrum excited at 258 nm. Additionally, the emission color of CaWO4:xDy3+ phosphors can be suitably tuned from blue to green, and finally to yellow by the modulation of excitation wavelength and Dy3+ ion concentration. Ultimately, these color-tunable phosphors may have potential applications in the fields of miniature color displays.

The temperature‐dependent device characteristics of InGaN/GaN near‐ultraviolet light‐emitting diodes, operating at λ ∼380 nm, with a chip size of 0.5 × 1 mm2 were reported. Their optical and spectral properties were measured and analyzed at different injection current levels and heatsink temperatures. The device performance showed the optical output power of 92.8 mW, forward voltage of 4.30 V, and emission peak wavelength of 380 nm at 350 mA and 298 K. The junction temperature (Tj) was experimentally estimated via the forward voltage method, leading to a thermal resistance of ∼10.03 K W−1. For comparison with the simulated Tj, the three‐dimensional steady‐state heat transfer simulation based on the finite element method was also carried out.

Mesoporous silica (JLU-20-S) is successfully synthesized at high-temperatures (180-220 °C) by an assembly of preformed silicalite-I zeolite nanoclusters with the mixture of triblock copolymer surfactant (P123) and fluorocarbon surfactant (FC-4). The preformed silicalite-I nanoclusters are obtained by heating, at 100-120°C for 2-3 h, silica gels at SiO 2 /(TPA) 2 O/H 2 O molar ratios of 1/0.14/36. Mesoporous JLU-20-S shows extraordinary stability in steam (800 °C, 4 hours), compared with other mesoporous silica materials (JLU-20 synthesized at 190 °C, MPS-9 prepared from preformed silicalite-I zeolite nanoclusters at 100 °C, and SBA-15). The results of X-ray diffraction and transmission electron microscopy show that JLU-20-S has a hexagonal mesoporous symmetry, and the data obtained from N 2 isotherms show that JLU-20-S contains both mesopores and micropores. The high steaming stability of the mesoporous silica of JLU-20-S is possibly related to synergistic advantages of both high-temperature synthesis and preformed zeolite nanoclusters in the synthesis of ordered mesoporous silica materials, and the observed microporous volume in JLU-20-S is attributed to the use of preformed zeolite nanoclusters.

We report the improved light output power in gallium nitride-based green flip-chip light-emitting diodes (FCLEDs) employed with inverted tetrahedron-pyramidal micropatterned polydimethylsiloxane (ITPM PDMS) films as an encapsulation and protection layer. The micropatterns are transferred into the surface of PDMS films from the sapphire substrate master molds with two-dimensional periodic hexagonal TPM arrays by a soft imprint lithography method. The ITPM PDMS film laminated on the sapphire dramatically enhances the diffuse transmittance (T(D)) in a wavelength (λ) range of 400-650 nm, exhibiting the larger T(D) value of ~53% at λ = 525 nm, (cf., T(D) ~1% for planar sapphire). By introducing the ITPM PDMS film on the outer surface of sapphire in FCLEDs, the light output power is enhanced, indicating the increment percentage of ~11.1% at 500 mA of injection current compared to the reference FCLED without the ITPM PDMS film, together with better electroluminescence intensity and far-field radiation pattern.