High color rendering index and chromatic-stable white organic light-emitting diodes with single-host double emissive layer structure

In this paper, we successfully demonstrated high color rendering index (CRI) and color stable white organic light-emitting diodes (WOLEDs) based on a hole-type single-host double emissive layer (EML) structure. By combining the yellow phosphorescent emission with the blue monomer and red excimer emission of platinum [1,3-difluoro-4,6-di(2-pyridinyl)benzene]chloride (Pt-4), the devices exhibited a maximum CRI of 93, which was attributed to the perfect spectrum complement and the relative intensity adjustment of each emission peak. Meanwhile, the WOLEDs were very stable and showed a slight color coordinate shift of (+/- 0.007, +/- 0.004) over a wide range of driving voltages from 4 to 10V. The use of the double EML structure effectively confines the exciton generation zone in the Pt-4 EML, thus, the white-light emission comes from the energy transfer from host to Pt-4 and then to yellow phosphor, which is less affected by the driving conditions.