Multiple Emission Mechanism Based Four-Peak Tuning Strategy To Achieve Ultra-High Color Rendering Index And Chromatic-Stable White Organic Light Emitting Diodes

We successfully fabricated white organic light-emitting diodes(WOLEDs) based on double light-emitting layers (EMLs) with ultra-high color rendering index (CRI)and stable chromaticity by multiple mechanism four peaks tuning. The phosphorescent blue monomer and red excimer emission from Platinum [1,3-difluoro-4,6-di (2-pyridinyl) benzene]chloride(Pt-4) together with the deep blue fluorescence and yellow phosphorescence emission from a co-emission light-emitting layer realized excellent four-peak tuning WOLEDs. Ultra-high CRI of 94 and extremely stable Commission Internationale deL'Eclairage (CIE) coordinates of (0.420 +/- 0.003,0.360 +/- 0.002) over a wide voltage range were presented. The high CRI is ascribed to broad and continuous four peaks emission covering the fully visible spectrum. The mixed bipolar interlayer effectively control the distribution of excitons in the two regions of emission, which makes the chromaticity of WOLEDs extremely stable. Also the stable emission mechanism of two EMLs contribute to chromatic stability. Significantly, the devices showed high efficiency under the premise of high CRI and stable chroma by effective strategic of structural design.