Electroluminescence of Conjugated Aromatic Polymers in Organic Light Emitting Diodes

Organic electroluminescent materials have been the subject of intense research for use in light emitting diodes (LEDs). When compared with liquid crystal displays (LCDs), organic light emitting diodes (OLEDs) require lower energy input, have a wider viewing angle with improved color contrast, and can be made much thinner. The electroluminescence (EL) of organic compounds was first demonstrated in 1953 by Bernanose but was not significantly developed until 1987 when Tang and Van Slyke constructed a device employing aluminum tris(8-hydroxyquinoline) 1 as the luminescent material. The first example of a polymer-based OLED was published by Friend et al. in 1990 in which poly(p-phenylene-vinylene) (PPV) 2 was used as the emissive layer. Since this discovery, many conjugated polymers have been developed for use in LEDs including poly(1,4-phenylene) (PPP) 3, poly(thiophene) 4, and polyfluorene 5.