Effect of electron injection and transport materials on efficiency of deep-blue phosphorescent organic light-emitting devices

We investigate the performance of FIr6-based deep-blue phosphorescent organic light-emitting devices (PHOLEDs) with three different electron transport materials, bathocuproine (BCP), 4,7-diphenyl-1,10-phenanthroline (BPhen), and tris[3-(3-pyridyl)mesityl]borane (3TPYMB), and study the effect of doping alkaline metals (Li and Cs) into these charge transport materials. External quantum efficiency (ηEQE) of (20 ± 1)% and peak power efficiency (ηP) of (36 ± 2) lm/W were achieved maintaining Commission Internationale de L’Eclairage (CIE) coordinates of (x = 0.16, y = 0.28) in p-i-n dual-emissive-layer (D-EML) deep-blue PHOLEDs with 3TPYMB as the electron transport material and 3TPYMB:Cs as the electron injection layer. The high efficiencies are attributed to the high triplet energy of 3TPYMB as well as the increased conductivity of 3TPYMB:Cs.