Efficient full-colour electroluminescence and stimulated emission with polyphenylenes

Abstract Soluble and stable polyparaphenylene-type ladder polymers (LPPPs) with an extraordinarily high degree of intrachain order and exceptionally low concentration of defects belong to the class of best-defined conjugated low-dimensional organic semiconductors currently available. Parahexaphenyl, the highly stable oligomer of polyparaphenylene, can be synthesized in the form of single crystals, disordered thin films and highly ordered epitaxially grown thin films. We demonstrate the fabrication and characterization of highly efficient red-green-blue (RGB) and white light-emitting devices with these electroactive materials. These RGB devices are fabricated based on a new technique, which allows the realization of full-colour flat-panel displays. Using this new technique, we are able to produce devices having any desired emission colour in the visible and near-infrared spectrum. An efficient white-light emission is generated by an internal excitation energy (Forster-type) transfer from the blue LPPP component to a red light-emitting polymer in a polymer blend, which is used as the active layer in a light-emitting diode. We present an optically pumped methyl-substituted LPPP waveguide, laser structure, which shows a spectrally very narrow and highly directional blue-green light output.