For multicolor display applications, polymeric light emitters of the three primary colors of red, green and blue are required. Emitters of high luminescence efficiency and long lifetime stability for red and green have been found, but the search for a suitable blue emitter continues. 2,7-Disubstituted dibenzosilole monomers have been prepared by the selective translithiation of 4,4'-dibromo-2,2' diiodobiphenyl followed by silylation with dichlorodihexylsilane. Suzuki copolymerization of dibromo and bis(boronate) monomers afforded poly(9,9-dihexyl-2,7-dibenzosilole) which showed better color stability and efficiency than the corresponding polyfluorene in a single layer light emitting device. Preliminary studies demonstrated this to be a promising blue light emitting polymer.
Electroluminescence from conjugated polymers can be significantly improved by harnessing the energy of their nonemissive triplet states. Poly(2,7-dibenzosilole) has been prepared and its triplet energy has been measured as 2.14 eV, a figure that is slightly higher than that of polyfluorene (2.09 eV). Two new tris-cyclometalated iridium complexes with blue-to-green emission properties have been prepared and characterized.