Synthesis and properties of new poly(terfluorene) derivatives containing spirobifluorene and electron transport groups for stable blue electroluminescence

We have synthesized three new blue-emitting poly(terfluorene) derivatives containing spirobifluorene and electron transport groups (quinoline or oxadiazole). The strategy is to connect the monomers via positions 2 and 2' of spirobifluorene, which significantly restricts the interchain interaction and effectively adjusts the conjugation length. The incorporation of electron-deficient units (quinoline or oxadiazole) into the positions 7 and 7' of spirobifluorene tunes the emission band and reduces the lowest unoccupied molecular orbital energy level. Blue electroluminescence with narrow emission was achieved in the devices of ITO/PEDOT/polymer/Ca/ A1. The maximum luminances are in the range of 102-235 cd/m(2) and the maximum photometric efficiencies are in the range of 0.17-0.21 cd/A. All the polymers show good spectral stability, and are promising for use as stable blue-emitting or electron-transport/injection materials in polymeric light-emitting diodes. (c) 2005 Wiley Periodicals, Inc.