Light emitting polymers photoconduction

The photoconductivity of polysilanes was described in Section 5.8, and their electroluminescence is covered in Section 5.9.2. These properties make polysilanes possible components of polymer light-emitting diodes, either as charge transport layers or as the actual emissive materials.146 A drawback of the polysilanes is their photodegradation under ultraviolet irradiation, a problem which must be overcome if polysilanes are to become commercially useful. 

Despite the extensive application of ruthenium complexes in DSSC, transition metal containing polymers have received relatively little attention in the fabrication of polymeric photovoltaic cells. Most of the early works on ruthenium containing polymers were focused on the light-emitting properties.58-60 Several examples of ruthenium terpyridine/bipyridine containing conjugated polymers and their photoconducting/electroluminescent properties were reported.61,62... 

Osaheni and Jenekhe reported a synthesis of conjugated rigid-rod polymers and their NMR data. The conjugated rigid-rod polymers have interesting photoconductive, light-emitting and third-order nonlinear optical properties that have some potential for applications in optoelectronics and photonics. 

Since 1992 when the first edition of the Handbook of Polymer Synthesis was published a number of new applications for photoconductive polymers or, to put it correct, charge transport materials, have appeared. The most successful development are organic light emitting diodes (OLEDs) whieh right now enter the market as bright displays for cellular phones and ear radios. Other imortant areas are organie field effect transistors, solar cells and lasers. 

In oligomers and polymers, neutral excited states, or excitons, can be produced by photo-excitation or charge recombination (capture of electrons and holes in LEDs). These can either decay radiatively, as desired for light-emitting diodes or nonradia-tively, with the possibility of yielding mobile charge carriers, for photoconductive and photovoltaic cells. 

Photoconductivity is based on the conversion of light to electricity. The reverse phenomenon, electroluminescence, is based on the conversion of electricity to light. Electroluminescence is useful for flat-panel display and 11-VI semiconductors such as ZnS are employed for this purpose [132], The current trend is toward the development of polymeric electroluminescent material for their processing flexibility [133,134]. It has already been demonstrated that properly doped semiconductor nanoclusters such as ZnIMn1 IS emits light efficiently [135], With the demonstration of photoconductivity [101 103] these nanocluster-doped polymers can become interesting candidates of electroluminescent materials. No experimental work has been performed yet. 

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