All fluorescent and high color rendering index white organic light-emitting devices with improved color stability at high brightness

We have demonstrated high color rendering index (CRI) white organic light-emitting devices using a multilayer structure based on all fluorescent emitters. The CRI of white light can be easily tuned by adjusting the thickness of the blue emitting layer (B-EML). In particular, the device with 8-nm-thick B-EML obtains very high CRI values (91-92) over a wide range of luminance (4000-23,000 cd/m2). Furthermore, the Commission Internationale De L'Eclairage coordinates of the device is rather stable and the variation is only (± 0.005, ± 0.003) over 4000-23,000 cd/m2. The values are very close to white light equivalent energy point of (0.333, 0.333). We attribute these unique performances to the competition of the two mechanisms of the carrier trapping of the red dopant and efficient förster energy transfer in the blue emitting layer.