Kaiwen Xue

Dramatic efficiency improvement in single-layer orange phosphorescent organic light-emitting devices with suppressed efficiency roll-off

We have successfully demonstrated efficient single-layer organic light-emitting devices (OLEDs) with a current efficiency of 31.38 cd A−1. The efficiencies still remain as high as 31.36 cd A−1, 30.76 cd A−1 and 29.98 cd A−1 at the luminance of 1000 cd m−2, 5000 cd m−2 and 10 000 cd m−2. The key feature of the device concept is uniformly doping iridium-bis-(4,6-difluorophenyl-pyridinato-N,C2)-picolinate (FIrPic) into a single organic layer to balance the transport of charge carriers. To better understand the mechanism of single-layer OLEDs, the position of the recombination zone and the influence of FIrPic on the transport properties are also studied in detail. Our work clearly reveals that the performance of the single-layer OLEDs can be dramatically improved by intentionally doping with a phosphorescent dye to balance the transport of charge carriers. This novel and versatile device concept provides a promising simple method to achieve high performance single-layer OLEDs.

Efficient white phosphorescent organic light-emitting diodes consisting of orange ultrathin and blue mixed host emission layers

We have successfully demonstrated highly efficient white phosphorescent organic light-emitting diodes (OLEDs) by inserting an ultrathin non-doped orange layer within blue mixed host emission layer. The key feature of the novel device is the employment of blue mixed host and orange ultrathin layers, resulting in an extended recombination region and more balanced charge carrier. The maximum efficiencies of 33.8 lm W−1 and 32.2 cd A−1 are obtained. Moreover, the resulting white device achieves a slight efficiency roll-off and a high luminance at low operating voltage. Our versatile concept suggests a promising simple method to achieve high performance white OLEDs.

Improved performance for white phosphorescent organic light-emitting diodes utilizing an orange ultrathin non-doped emission layer

Efficient white phosphorescent organic light-emitting diodes with excellent stable spectra based on an orange ultrathin non-doped layer and a blue doped emission layer are reported. The emission color can be changed by adjusting the thickness of the 4,4′-bis(carbazol-9-yl)biphenyl (CBP) layer or the mixed ratio of CBP and 2,2′,2′′-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) in the mixed interlayer. On the basis of the mixed CBP:TPBi interlayer, we successfully fabricated a white device with superior stable spectra and lower turn-on voltage. Moreover, the white device with an optimum mixed ratio of 2 : 1 in the mixed interlayer has a power efficiency of 40.1 lm W−1, which is 2.1 times as high as that of the device with a pure CBP spacer.