High brightness stable white and yellow light-emitting diodes from ambipolar polyspirofluorenes with high charge carrier mobility

We have used two polyspirofluorenes, spirodiethylhexyloxylpolyfluorene (spiro-diEHPF) and triphenylamine-grafted spirodiethylhexyloxylpolyfluorene (spiro-TPA50-diEHPF), which exhibit rather high charge mobilities in the order of 10−3–10−4cm2∕Vs. The light-emitting devices with rubrene-doped spiro-diEHPF show maximal luminances of 36 000 and 70000cd∕m2 with maximal efficiencies 3.5 and 9cd∕A for the white and yellow emissions, respectively. For rubrene-doped triphenylamine-grafted polymer, spiro-TPA50-diEHPF, the maximal luminances and efficiencies are 56000cd∕m2 and 9cd∕A for white-emitting devices and 72000cd∕m2 and 14cd∕A for yellow emission. Furthermore, the electroluminescence profiles of the investigated devices show nearly independent of the applied voltages.