Correlation of charge trapping and charge transport properties of blue triplet emitters with device performances of blue phosphorescent organic light-emitting diodes

• Significant electron trapping by blue phosphorescent dopant materials.
• Little hole trapping by blue phosphorescent dopant materials.
• High driving voltage by electron trapping in blue device.

The relationship between driving voltage and charge trapping in blue phosphorescent organic light-emitting diodes was investigated using two blue phosphorescent emitters based on fluorine substituted phenylpyridine ligands. It was demonstrated that electron trapping by dopant reduces electron current density in the emitting layer, while hole trapping had little effect on the hole current density in the emitting layer. It was found that the electron trapping by phosphorescent dopant was the dominant factor for the driving voltage of blue phosphorescent organic light emitting diodes.

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