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 10 V. 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.