White emitters

The simulation discussed above was based on full color produced by individual red, green, and blue emitters. Other full-color reproduction approaches have been proposed for OLED displays including color from blue emitter by means of energy down conversion fluorescent filter [177], and color from white emitters by means of transmission color filter sets similar to that used in LCD industry [178,179]. Table 1.5 compares the EL efficiency of equivalent white... 

Color from red, green, and blue emitters Color from blue emitter with phorsphor filters Color from white emitter with transmission filters... 

M Kashiwabara, K Hanawa, R Asaki, I Kobori, R Matsuura, H Yamada, T Yamamoto, A Ozawa, Y Sato, S Terada, J Yamada, T Sasaoka, S Tamura, and T Urabe, Advanced AM-OLED Display Based on White Emitter with Microcavity Structure. SID 04, Digest, 1017-1019, 2004. 

Bis(2-(2-hydroxphenyl)benzothiazolate)zinc(II) (Zn(BTZ)2, 85) is an excellent white emitter. The HOMO and LUMO energy levels of Zn(BTZ)2 are —5.41 eV and —2.65 eV, respectively. Just as was found by Zuppiroli et al. for Znq2 derivatives, Zhu et al., found that the electron transport of Zn(BTZ)2 is better than Alq3, though the electron injection barrier is higher for Zn(BTZ)2 [136]. This has been explained by the strong intermolecular interaction of Zn(BTZ)2 molecules. This same group has examined the use of Zn(BTZ)2 as an ETM in PLEDs and the results are consistent with those with SMOLEDs [137]. 

Metal complexes with Schiff base ligands have useful applications in organic optoelectronics due to their outstanding photoluminescent (PL) and electroluminescent (EL) properties, and their ease of synthesis, which readily allows structural modification for optimization of material properties.28 Hamada and co-workers pioneered the use of zinc(II) Schiff base complexes as blue to greenish white emitters for EL devices. We have demonstrated Pt(II) Schiff base triplet emitters as yellow dopants for organic light-emitting devices... 

Based on the above study, Schnick et al. believe that the observed feature makes BasPsNioBr u " a promising candidate for use as a single white emitter in pcLEDs. Moreover, the development ofBasPsNioBr u " demonstrated that nitridic zeolites are well suited as host lattices for high-performance luminescence mate-... 

Eluorescent lamps for showing plants use a blue-white phosphor blended with a deep red-emitting phosphor. This more closely corresponds to the action spectmm for plant growth because there is Htfle green in the spectmm, African violets, for example, have leaves which appear more purple in color. The deep red emitter which is commonly used is magnesium fluorogermanate activated by Mn. ... 

The fluorescence color converter technique [32] can, in principle, overcome much of this power loss by replacing the white light emitter with a blue-emitting organic stack, and the absorbing filters with green and red fluorescent dyes. Thus when a green pixel is desired, the OLED underneath is turned on and the blui... 

White, E. H., and Roswell, D. F. (1991). Analogs and derivatives of firefly oxyluciferin, the light emitter in firefly bioluminescence. Photochem. Photobiol. 53 131—136. 

Thus, we have two units of measurement of intensity. One is related to scattering from a surface, L, i.e.- in foot-lamberts and the other is related to emittance, H, i.e.- in lumens per square foot. Although we have assumed "white" light up to now, either of these two can be wavelength dependent. If either is wavelength dependent, then we have a pigment (reflective- but more properly called scattering) with intensity in foot-lamberts, or an emitter such as a lamp or phosphor (emittance) with intensity in lumens. 

If we have a certain color, a change in intensity has a major effect on what we see (in both reflectance and emittance). For example, if we have a blue, at low intensity we see a bluish-black, while at high intensity we see a bluish-white. Yet, the hue has not changed, only the intensity. This effect is particularly significant in reflectance since we can have a "light-blue" and a "dark-blue", without a change in chromaticity coordinates. 

Soft, silver white metal that is isolated in the tiniest of amounts. All isotopes are radioactive, the longest-lived has a half-life of 22 years. The element is an intermediate in the decay series of 235U. Strong alpha emitter that is used in radioactivation analysis and forms an effective neutron source with beryllium. 

This soft, silver white metal reacts with air and water. The oxide is applied in optical glasses with high refractive indices (special lenses for powerful cameras and telescopes). Used for special effects in optoelectronics and electronics. Lanthanum exhibits catalytic properties. It is a component of flint and battery electrodes. Lanthanum boride (LaB6) is the superior electron-emitter for electron microscopes. Lanthanum is the first of the series of 14 lanthanides, also called the "rare-earth" metals, whose inner N shells are filled with electrons. They do not belong on the "red list" of endangered species they are neither rare nor threatened with depletion. China is particularly rich in lanthanide ores. 

Silvery white, artificial element that is also generated by intensive bombardment of plutonium with neutrons. It is a strong ("hot") neutron emitter and is used in microgram quantities in nuclear medicine. This reliable neutron source is also used in industry and science (for activation analysis). 

Strictly, a black body is defined as something that absorbs photons of all energies, and does not reflect light. Furthermore, a black body is also a perfect emitter of light. A black body is a theoretical object since, in practice, nothing behaves as a perfect black body. The best approximations are hot objects such as red- or white-hot metals. 

Figure 16. a) Electroluminescence of the reference system PVK/BND (left) and the white-light emitter PVK/THP/BND (right), b) Device configuration. 

The performance of AMOLEDs is improved drastically in the past years. In contrast to the data shown in Table 1.2 (which representing development stage in 2002), a set of recent data of a 14.1" WXGA AMLCD made with solution-processed OLED emitters is shown in Table 1.3 [163,175,176], The color gamut is improved to over 60% with respect to NTSC. The luminous and power efficiencies at white point (x 0.28, y 0.31) are >8 cd/A and >5 lm/W. The power efficiency surpasses the performance of AMLCDs, plasma displays, and all other known flat-panel displays in commercial market or under development. A photo of the 14.1" AMOLED display is shown in Figure 1.25b. 

J Kido, K Hongawa, K Okuyama, and K Nagai, White light-emitting electroluminescent devices using the poly(Y-vinylcarbazolc) emitter layer doped with three fluorescent dyes, Appl. Phys. Lett., 64 815-817, 1994. 

The simplest method yet most complex structure for white OLEDs consists of three primary emission colors blue, green, and red. Kido et al. reported using three emitter layers with different carrier transport properties to produce a white emission [273], The multilayer structure of such an OLED is ITO/TPD/p-EtTAZ/Alq3/Alq3 Nile Red/Alq3/Mg Ag, in which a blue emission from the TPD layer, a green emission from the Alq3 layer, and a red... 

White emission can also be achieved by directly combining a blue emitter and an orange-red emitter as codopants. The combination of blue and orange-red emission generates white emission. 

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