High efficiency warm-white organic light emitting diodes from a single emitter in graded-doping device architecture

We report high efficiency single-emitter white organic light emitting diodes (SWOLEDs) from a phosphorescent platinum-pyridyltriazolate complex. We have demonstrated good control of the recombination zone and its impact on device performance by adjusting the number of emissive layers, their thicknesses and relative positions in the device stack. Device optimization has resulted in SWOLEDs with a peak power efficiency (PE) = 30.4 ± 1.3 lm/W, external quantum efficiency = 17.0% ± 0.1%, and correlated color temperature = 3450 K, within acceptable warm-white range despite the color rendering index being only 62. The devices exhibit negligible performance roll-off at 500–1000 cd/m2.