Optical light emitting diodes-physical properties

Optical properties light-emitting diodes, resonance absorption of near IR-radiation Physical and chemical properties large specific surface and possibihty of surface chemical modification, adsorbents, catalysts, chemical sensors, materials for electrodes, chemical batteries, fuel elements and super condensers. 

The physical mechanism by which semiconductor light-emitting diodes (LEDs) emit light is spontaneous recombination of electron-hole pairs and simultaneous emission of photons. The spontaneous emission process is fundamentally different from the stimulated emission process occurring in semiconductor lasers and superluminescent LEDs. The characteristics of spontaneous emission that determine the optical properties of LEDs will be discussed in this section. 

One active area of research is completely missing. These are the optical and electrical properties, with effects such as the high conductivity of doped conjugated polymers, electro-luminescence in polymeric light emitting diodes, or the ferro- and piezoelectricity of poly(vinylidene fluoride), to cite only a few examples. There is no good reason for this omission, only that I did not want to overload the book with another topic of different character which, besides, mostly employs concepts which are known from the physics of semi-conductors and low molar mass molecules. 

The commercial application of polymer blend technology has grown significantly such that, today, compositions are available with properties that once were substantially unattainable with homopolymers. To date, polymer blends have been applied in optical fibers [13,14], microlenses [15], liquid crystal display components [16,17], solar cells [18-20], nonionizing radiation detection [21] and polymer light-emitting diodes [22-24]. In particular, the use of developed polymer blends in optoelectronics applications appears unlimited. Polymer blends may also provide model systems in statistical physics when studying the fundamental aspects of equilibrium and nonequilibrium properties [3], optical properties [25], and mechanical and electrical properties [26]. 

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