High-efficiency turquoise-blue electrophosphorescence from a Pt(II)-pyridyltriazolate complex in a phosphine oxide host

We demonstrate high-efficiency turquoise-blue electrophosphorescence from bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) [Pt(ptp)(2)] doped in 4-(diphenyl-phosphoryl)-N, N-diphenylaniline (HM-Al). Organic light-emitting diodes (OLEDs) with 5% Pt(ptp)(2):HM-A1 attain peak power efficiency of 61.2 lm/W, versus 40.8 lm/W for analogous devices employing the standard turquoise-blue phosphor bis[4,6-difluorophenyl)-pyridinato-N,C-2'](picolinato)iridium(III) (FIrpic). Devices with x% Pt (ptp)(2): HM-A1 exhibit blue emission maxima (lambda(max) similar to 480 nm) with monotonic increase in excimer/monomer intensity ratio at higher doping levels within 1%-10%, causing color shift toward green and less charge balance. This work represents a significant step toward optimizing future white OLEDs from the same phosphor via combination of low-doped and higher-doped or neat films. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3268434]