Blue Phosphorescent Organic Light‐Emitting Diodes Using N‐Type Semiconductor Extra Emission Layer

Blue phosphorescent organic light‐emitting diodes (PHOLEDs) are fabricated using n‐type and bipolar extra emission layer with structure of ITO/TAPC (700 Å)/mCP:FIrpic‐8% (250 Å)/mCP:x:FIrpic‐8% (50 Å, x: CDBP, TPBi, TmPyPB)/TPBi (300 Å)/LiF (20 Å)/Al (1200 Å). The electrical and optical characteristics of blue PHOLEDs with different extra emission layer (EEL) material located between EML and ETL such as current density, luminous efficiency, efficiency roll‐off, and EL spectra are observed and proven that the extra emission layer material trapped charge carrier. The blue PHOLED with TPBi EEL improved driving voltage, luminous efficiency, and efficiency roll‐off compared to reference blue PHOLED without EEL.