Organic/polymer LEDs

Schoo, H.F.M., et al. 1997. Organic polymer LEDs with mobile and immobile ions. Macromol Symp 125 165. 

Over the past 50 years there have been major changes in theories of the nature of the silica in the conventional alkali silicate solutions with Si0j Na20 ratios from 2 1 to 4 1. The physical similarity of viscous, stringy solutions of soluble silicates to solutions of linear organic polymers led in some cases to the supposition that vis-... 

Polymer LEDs are similar to thin film organic molecular LEDs first reported in 1987 17). Organic molecular LEDs utilize thin films of small organic molecules rather than polymer films as the light-emitting layer. The films of small organic molecules are undoped and have electronic properties comparable to the polymer films used in polymer LEDs. In general, the device physics of polymer LEDs is... 

The utility and importance of multi-layer device structures was demonstrated in the first report of oiganic molecular LEDs [7]. Since then, their use has been widespread in both organic molecular and polymer LEDs [45, 46], The details of the operating principles of many multi-layer structures continue to be investigated [47—49], The relative importance of charge carrier blocking versus improved carrier transport of the additional, non-luminescent layers is often unclear. The dramatic improvements in diode performance and, in many cases, device lifetime make a detailed understanding of multi-layer device physics essential. 

This chapter is organized as follows in Section 11.2 the relevant properties of electroluminescent polymer Films are summarized in Section 11.3 the electronic properties of mctal/polymer junctions are described in Section 11.4 single layer polymer LEDs are discussed in Section 11.5 multi-layer polymer LEDs are considered and Section 11.6 summarizes the conclusions. 

Polyphosphazene films could also be modified very easily by grafting organic polymers onto the surface using chemical, photochemical or y-radiolytic processes. In almost all cases these studies led to the increase in the surface hy-drophilicity and biocompatibility of the phosphazene films without depressing their bulk features. 

Advances in clay-bearing formation treatment have led to the development of numerous clay-stabilizing treatments and additives. Most additives used are high-molecular-weight cationic organic polymers. However, it has been shown that these stabilizers are less effective in low-permeability formations [834]. 

The use of organic polymers as conductors and semiconductors in the electronics industry has led to a huge research effort in poly(thiophenes), with a focus on the modification of their electronic properties so that they can behave as both hole and electron conductors. Casado and co-workers [60] have performed combined experimental and theoretical research using Raman spectroscopy on a variety of fluorinated molecules based on oligomers of thiophene, an example of one is shown in Figure 7. 

There is no reason why the same principle cannot be applied for light-emitting polymers as host materials to pave a way to high-efficiency solution-processible LEDs. In fact, polymer-based electrophosphorescent LEDs (PPLEDs) based on polymer fluorescent hosts and lanthanide organic complexes have been reported only a year after the phosphorescent OLED was reported [8]. In spite of a relatively limited research activity in PPLEDs, as compared with phosphorescent OLEDs, it is hoped that 100% internal quantum efficiency can also be achieved for polymer LEDs. In this chapter, we will give a brief description of the photophysics beyond the operation of electrophosphorescent devices, followed by the examples of the materials, devices, and processes, experimentally studied in the field till the beginning of 2005. 

Concerns about the effect of TPP on eutrophication have led many states, cities, and regional governments to ban the use of the compound in syndets. Such bans have caused serious problems for detergent manufacturers, however, because no entirely satisfactory substitute for TPP has yet been found. Two promising candidates are the sodium salt of nitrilotriacetic acid, 3Na, N(CH2C02)3 , or NTA and ethylenediaminetetraacetic acid (EDTA). Both of these compounds act in much the same way as TPP, that is, by sequestering metal ions. Other builders that have been incorporated into syndet formulations include sodium carbonate, synthetic zeolites, borates, and organic polymers known as polycarboxylates. 

It is well known that polysaccharide cellulose is - in general - a very important and fascinating biopolymer and an almost inexhaustible and sustainable polymeric raw material. The trend towards renewable resources and the tailoring of innovative products for science, medicine, and technology has led to a global renaissance of interdisciplinary cellulose research and the use of this abundant organic polymer over the last decade [1]. 

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