Electron-transporting layer effects on blue phosphorescent organic light-emitting diodes

In this work, we demonstrated the electron-transporting layer (ETL) effects on device electroluminescence (EL) performance of blue phosphorescent organic light-emitting diodes (PhOLED). Three well known electron-transporting materials such as 3-(4-biphenyl-yl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ), diphenyl-bis[4-(pyridin-3-yl)phenyl]silane (DPPS) and 1,3,5-tri( m-pyrid-3-yl-phenyl)benzene (TmPyPB) were employed as ETL inside a blue PhOLED. The material properties of these three ETL materials individually dominated the different location of carrier recombination and exciton formation inside device, especially carrier mobility. By investigating the EL performance of these three devices, one can be concluded that high carrier mobility ETL results to a low driving voltage, worse carrier confinement in the emitting layer, greater amount of leakage electrons. The great efficiency performance is dominated by the great carrier confinement in the emitting layer.