Tungsten oxides (WOx) films have gained promising attention in terms of selective solar absorption due to its high intrinsic absorption properties. We fabricated a series of single-layer WOx films on aluminum substrates by a magnetron sputtering system. The optical absorption properties of the film were investigated by spectrophotometer and ellipsometry. We found that the optical properties of the film were very sensitive to the change of the thickness. The result showed the highest α value can reach up 0.82 with the thickness of 26 nm at 0.6 Pa or 70 nm at 1.5 Pa, and both ε values was around 0.05, indicating the high spectral selectivity properties. The different reflectance evolutions presented a wide range of color appearances, such as yellow, reddish, cyan, and blue. Moreover, the surface morphologies and phase structures of single-layer WOx films were investigated by SEM, XRD, and Raman. A WOx/SiO2 solar selective absorber coating indicated that the as-obtained WOx film was a promising application in solar-thermal conversion. 相似文献
The novel chiral conjugated polymers P‐1 and P‐3 are prepared from the monomers S‐M‐2 and S‐M‐3 with (R,R)‐1,2‐aminocyclohexane ( M‐1 ) via a nucleophilic addition–elimination reaction, respectively. The Eu(III)‐grafting chiral polymers P‐2 and P‐4 could be obtained by direct coordination reaction of Eu(TTA)3·2H2O with P‐1 and P‐3 , respectively. Photoexcitation of P‐2 produces pink color emission as a result of the combination of partial blue self‐emission chromophore of P‐1 along with the red color from the Eu(TTA)3 moiety, whereas P‐4 shows the exclusively red color emission from the Eu(III) (5D0→7F2) transition due to almost complete excitation energy transfer from the macromolecular chain to the Eu(TTA)3 moiety. The choice substitution of phenyl derivative of the polymer plays a crucial role on the efficient energy transfer from the polymer chain to Eu(III) ion center. Meanwhile, the glum value of the dissymmetry factor of circularly polarized luminescence (CPL) for the 5D0→7F2 transition of Eu(III) for P‐4 reaches as high as +0.0207, whereas P‐2 exhibits the largest glum value about +0.0464 centered at 434 nm.
We demonstrate molecular organic white light-emitting devices (LEDs), using vacuum-deposited thin films of N,N-diphenyl-N,N-bis(1-naphthyl)-(1,1-biphenyl)-4,4-diamine (NPB) as the hole-transporting layer, 1,6-bis(2-hydroxyphenyl)pyridine boron complex ((dppy)BF) as the emitting layer, tris-(8-hydroxyquinoline)aluminum (Alq) doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as the red-emitting layer. The white light comes from three components: exciplex emission at the interface between NPB and (dppy)BF, which covers the wide range from 500 to 700 nm, blue emission from bulk NPB and (dppy)BF and red emission from DCJTB. The chromaticity of the devices can be tuned by varying the thickness of (dppy)BF and doped Alq layers. The Commission Internationale De L'Eclairage (CIE) coordinates of emitted light vary from (0.31, 0.335) to (0.32, 0.345) when forward voltages change from 10 to 20 V, which are just adjacent to the white-light equi-energy point (0.33, 0.33). The brightness and luminous efficiency are 150 cd/m2 and 0.3l m/W at 12 V, respectively. 相似文献
In the present article, the role of charge compensator ions (R+?=?Li+, Na+ and K+) in europium-doped strontium aluminate (SrAl2O4:Eu3+) phosphors was synthesized by the high-temperature, solid-state reaction method. The crystal structures of sintered phosphors were in a monoclinic phase with space group P21. The trap parameters which are mainly activation energy (E), frequency factor (s) and order of the kinetics (b) were evaluated by using the peak shape method. The calculated trap depths are in the range from 0.76 to 0.84?eV. Photoluminescence measurements showed that the phosphor exhibited emission peak with good intensity at 595?nm, corresponding to 5D0–7F1 (514?nm) orange emission and weak 5D0–7F2 (614?nm) red emission. The excitation spectra monitored at 595?nm show a broad band from 220 to 320?nm ascribed to O–Eu charge-transfer state transition and the other peaks in the range of 350–500?nm originated from f–f transitions of Eu3+ ions. The strongest band at 394?nm can be assigned to 7F0–5L6 transition of Eu3+ ions due to the typical f–f transitions within Eu3+ of 4f6 configuration. The latter lies in near ultraviolet (350–500?nm) emission of UV LED. CIE color chromaticity diagram and thermoluminescence spectra confirm that the synthesized phosphors would emit an orange-red color. Incorporating R+?=?Li+, Na+ and K+ as the compensator charge, the emission intensity of SrAl2O4:Eu3+ phosphor can be obviously enhanced and the emission intensity of SrAl2O4:Eu3+ doping Li+ is higher than that of Na+ or K+ ions. 相似文献