Organic White Light-Emitting Diodes Using Fluorescent and Phosphorescent Materials for Color Tunable Devices

Abstract

First, we investigated the transient characteristics of poly(9,9-dioctylfluorene)(PFO)-based polymer OLEDs (PLEDs) doped with green emissive phosphor fac-tris(2-phenylpyridine)iridium(III) [Ir(ppy)3] and red emissive phosphor tris(1-phenylisoquinoline)iridium(III) [Ir(piq)3] by applying the voltage pulse on the devices, and achieved the maximum luminance of 4800 cd/m2 and the ideal white emission with the Commission Internationale de L’Eclairage (CIE) coordinates of (0.33, 0.35) at the pulse width and frequency of 100 ns and 1 kHz, respectively. Especially, the CIE coordinates can be tuned from (0.25, 0.29) to (0.51, 0.40) by varying pulse width and frequency. Second, we investigated white OLEDs with blue emissive phosphor bis[(4,6-difluorophenyl)-pyridinato-N,C2] (picolinate)iridium(III) (FIrpic) and some red emissive materials. Using FIrpic and red emissive rare earth complex of tris(divenzoylmethane)-mono(4,7-dimethylphenanthroline) europium(III) [Eu(dbm)3phen] doped in poly(N-vinyl-carbazole) (PVK), the white emission of (0.31, 0.38) in the CIE coordinates was obtained at a current density of 0.5 mA/cm2. Utilizing the different transient characteristics between the host and dopant, emission color has been successfully tuned by varying the applied pulse width and frequency.