Stable and good color purity white light-emitting devices based on random fluorene/spirofluorene copolymers doped with iridium complex

Conjugated polymers PSNFP and PSNFF based on naphthalene-containing spirofluorene structure and 9,9-dioctylfluorene, 2,5-dioctylbezene were designed and synthesized for light emitting applications. These two polymers show good blue emission both in solution and thin film. Thermal gravimetric analysis reveals they have good thermal stability with the decomposition temperature higher than 400 °C. Electrochemistry characterization shows that both of these polymers have a large band gap and deep highest occupied molecular orbital, which are important features for phosphorescent host materials. White light-emitting diodes were fabricated by using PSNFF as the host material, containing two typical phosphorescent Ir complex dopants: green emitter Ir(mppy) ₃ and red emitter Ir(piq) ₂. The color coordinate CIE stayed nearly constant, changed from (0.32, 0.31) to (0.28, 0.31) when the current density varied from 2 to 20 mA cm ^-2.