Electro-optical properties

In this final subsection on OLEDs, we wish to show some selected, characteristic experimental results using the example of the multilayer OLEDs of the type shown in Fig. 11.9, and to explain them [10]. 

5 nm Ni anode is around 1.6 times higher than that of the OLED with the pure Ni anode. Such small differences are important for applications and can be discovered only by careful experimentation. A quantitative analysis of the results shown in Fig. 11.10 yields an external efficiency of Lo/j = 40cd/A for the OLED with the 

The level of quality that has been achieved in OLEDs can be seen also from their radiation characteristics Fig. 11.13 shows the angular distribution of the emitted intensity in a polar diagram for the multilayer OLED (Figs. 11.9 and 11.10). Its 

We shall not go further into the details of these experimental results here, but instead refer the reader to the original literature cited. These results are meant to give an example of the current state of development of OLEDs. 

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Barium sodium niobium oxide [12323-03-4] Ba2NaNb 02, finds appHcation for its dielectric, pie2oelectric, nonlinear crystal and electro-optic properties (35,36). It has been used in conjunction with lasers for second harmonic generation and frequency doubling. The crystalline material can be grown at high temperature, mp ca 1450°C (37). 

Experiments on transport, injection, electroluminescence, and fluorescence probe the spatial correlation within the film, therefore we expect that their response will be sensitive to the self-affinity of the film. This approach, which we proved useful in the analysis of AFM data of conjugated molecular thin films grown in high vacuum, has never been applied to optical and electrical techniques on these systems and might be an interesting route to explore. We have started to assess the influence of different spatial correlations in thin films on the optical and the electro-optical properties, as it will be described in the next section. 

Electro-Optical Properties of Bimetallic Nanoparticle-Doped Liquid Crystal Displays... 

An LCD is a ubiquitous electronic display. Now, it is widely distributed among human daily life, like mobile phones, TV, and personal computers. The LCD has, however, a drawback, i.e., slower response than a plasma display or an electroluminescene display. Recently we have first succeeded in combination of a nanoparticle technology with the LCD technology, which realized fast response of the LCD [45,235,236]. Thus we have found a phenomenon, i.e., a frequency modulation of the LCD doped with metallic nanoparticles. Since the frequency modulation, or electro-optic property depends on the kind of metals, we have prepared AgPd bimetallic nanoparticles protected with a typical liquid crystal molecule, 4-cyano-4 -pentylbiphenyl (5CB) to investigate the electro-optic property [45,235,236]. 

Fluorescent nanotubes of polyethyleneimine (PEI) and 3,4,9,10-perylenetetra-carboxylicdianhydride (PTCDA) have been prepared through the alternating deposition of polymers and small functional molecules that form covalent bonds (Figure 7.10) [ 120]. The nanotube synthesis starts with the deposition of P EI in the pores of an AAO membrane as the first layer. The PTCDA solutionis then used to bind to the PEI via covalent bonding (Figure 7.10). The electro-optical properties of the small molecule (PTCDA) are retained in the multilayer films of PEI/PTCDA. The prepared nanotubes retain their fluorescent properties for up to 10 months without... 

Commonly used material classes are the III-V compounds (especially when dynamic or active functions are needed), LiNbCh (because of its electro-optical properties), the indiffused glasses, the SiON-materials, the polymers and materials obtained from sol-gel technology. Last three will be treated in other chapters of this book. As an example we show the cross section of a simple channel structure based on SiON technology in Figure 6. 

Liquid crystals (LCs) have been the focus of considerable research for many years and have been developed for use in a wide array of applications. Recently, the development and application of polymer/LC composites has become an area of great interest in LC research. Introducing polymers in LC systems increases the inherent mechanical strength and may dramatically change the LC phase behavior and electro-optic properties (7). Conversely, the directional ordering present in liquid crystals forms a fascinating media in which to study polymerizations (2). 

Phase Behavior and Electro-optic Properties. With the great potential of PSFLCs, it is important to understand the changes induced by the polymer network on the FLC properties. In order to do so, two different non-mesogenic monomers, HDDA and PPDA, have been used. The structure of these monomers is quite similar (See Figure 1) with the only difference being that the phenyl group in PPDA is replaced with a six carbon alkyl chain for HDDA. These monomers, despite their structural similarity, have much different physical properties and consequently the polymers formed from HDDA and PPDA may also influence the FLC phase and electro-optic behavior differently. 

Although phase behavior is comparable for both HDDA and PPDA monomer mixtures, the electro-optic properties may behave quite differently. It has been shown previously that the polymer can considerably change PSFLC properties (1,34), but these changes are not the same for all polymers. To investigate the effects... 

The introduction of a polymer network into an FLC dramatically changes phase and electro-optic behavior. Upon addition of monomer to the FLC, the phase transitions decrease and after polymerization return to values close to that observed in the neat FLC. The phase behavior is similar for the amorphous monomers, HDD A and PPDA. The electro-optic properties, on the other hand, are highly dependent on the monomer used to form the polymer/FLC composite. The ferroelectric polarization decreases for both HDDA and PPDA/FLC systems, but the values for each show extremely different temperature dependence. Further evidence illustrating the different effects of each of the two polymers is found upon examining the polarization as both the temperature and LC phase of polymerization are changed. In PPDA systems the polarization remains fairly independent of the polymerization temperature. On the other hand, the polarization increases steadily as the polymerization temperature of HDDA systems is increased in the ordered LC phases. 

The electro-optic property of EO polymers comes from the NLO chromophores. When these chromophores are preferentially aligned to break the centrosymmetry of the material, the molecular level microscopic NLO effect of the molecules translates to the macroscopic second-order NLO effect of the polymer material. The poled material exhibits a strong macroscopic electro-optic effect. 

Liao, Y. Anderson, C. Y. Sullivan, P. A. Akelaitis, A. J. P. Robinson, B. H. Dalton, L. R., Electro optical properties of polymers containing alternating nonlinear optical chromophores and bulky spacers, Chem. Mater. 2006, 18, 1062 1067... 

S.-Y. Zhang, F. Kong, R. Sun, R.-K. Yuan, X.-Q. Jiang, and C.-Z. Yang, Synthesis, characterization, and electro-optical properties of a soluble conjugated polymer containing an oxadiazole unit in the main chain, J. Appl. Polym. Sci., 89 2618-2623, 2003. 

E-ct-phenylcinnamic acid, 6 edges, 281 EDX, 168 EDX analyses, 315 EELS, 223 eggshell, 277 eggshell repartition, 257 electrical conductivity, 8 electro-optical properties and quantum confinement,... 

Besides the direct electrical induction of electro-optical effects in liquid crystals, their activation by illumination of photoconductors could be of great technical interest. This method might well permit the electro-optical properties of nematic liquid crystals to be used on a larger scale, because photoconductor activation may eventually be applied to light amplification, optical data processing, and projection display systems, or used for recording phase-type holograms. 

Particles in the nanometer-size regime necessarily have large surface-to-volume ratios approximately one-third of the atoms are located on the surfaces of 40 A CdS particles, for example. Furthermore, colloid chemical preparations typically result in the development of surface imperfections and in the incorporation of adventitious or deliberately added dopants. Such surface defects act as electron and/or hole traps and, thus, substantially modify the optical and electro-optical properties of nanosized semiconductor particles. Altered photostabilities [595], fluorescence [579, 594, 596, 597], and non-linear optical properties [11, 598-600] are manifestations of the surface effects in colloidal semiconductors. 

The supporting medium (aqueous or organic solvents membrane-mimetic compartments) also has a profound influence on the optical and electro-optical properties of nanosized semiconductor particles. This dielectric confinement (or local field effect) originates, primarily, in the difference between the refractive indices of semiconductor particles and the surrounding medium [573, 604], In general, the refractive index of the medium is lower than that of the semiconductor particle, which enhances the local electric field adjacent to the semiconductor particle surface as compared with the incident field intensity. Dielectric confinement of semiconductor particles also manifests in altered optical and electro-optical behavior. 

Applications of Semiconductor Electro-Optical Properties to Chemical Sensing... 

Customarily, semiconductor surfaces are chemically or physically prepared to optimize their chemical and/or electro-optical properties. For chemical sensing applications, a freshly etched surface often provides greater chemical sensitivity. A Br2/MeOH etch of n-CdSe, for example, has typically yielded larger luminescence responses to analytes than have polished samples. Additionally, transducing films have been used to modify semiconductor surfaces to enhance the selectivity of CdSe for particular analytes [2]. 

The transducing mechanism of semiconductor luminescence involves the modification of the semiconductors surface electrical properties through molecular adsorption. Changes in solid-state electro-optical properties result from adsorption of the molecule of interest onto the semiconductor surface. 

From these results, As the particular tensor component of DAD molecular crystal is expected to be very high, more than 2-methyl-4-nitroaniline(MNA)(20), it would become one of the most suitable materials of highly efficient optical device for frequency doubler by using phase matching with optical wave guide. Electro-optical properties as well may be interesting. 

The concept of local perturbations of the director around nanoparticles, often linked to homeotropic anchoring to the nanoparticle surface, is a concept often brought forward in discussions of thermal, optical and electro-optic properties of nanoparticle-doped nematic liquid crystals, which adds a slightly different perspective to the invisibility of smaller particles in aligned nematics. This appears to be of particular relevance for particles coated with either hydrocarbon chains or pro-mesogenic as well as mesogenic units. 

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