To explain the origin of extremely high efficiencies of deep-blue fluorescent organic light-emitting diodes (OLEDs) with anisotropic-shaped anthracene derivatives, the enhancements of singlet-exciton generation efficiency and outcoupling efficiency were investigated by transient electroluminescence measurement and variable angle spectroscopic ellipsometry, respectively. Both the delayed fluorescence from singlet excitons generated via triplet-triplet annihilation and the outcoupling enhancement by dipole orientation of emitters were found to contribute to the high external quantum efficiencies of the devices. This dual efficiency enhancement is important for understanding and further improving high-performance fluorescent OLEDs.

We propose new dual core chromophore materials with blue emission. One of these derivatives, TP-AP-TP, exhibits a high luminance EQE value of 7.51% and twice the lifetime of a commercialized material, MADN. The dual core chromophore materials have narrower PL and EL spectra and better thermal properties than the single core chromophore materials. Author KeywordsOLEDs; Blue fluorescent emitting material; dual core chromophore; highly efficient material; Outcoupling effect; Singlet-exciton generation.

We introduced phenyl and naphthyl groups onto various positions of dual cores. Of the synthesized compounds, Na-AP-Na was found to exhibit the highest EL device efficiency of 5.46 cd A−1.