Optimization for tandem organic light-emitting diodes based on Firpic

Abstract

A series of single-unit and tandem blue phosphorescent organic light-emitting diodes (OLEDs) were prepared by adjusting the concentration of dopant based on the structure of ITO/NPB/EL unit/Alq₃/Cs₂CO₃/Al. The results show that tandem device with doping concentration of 10 wt% has appropriate energy transfer, which achieves the best performance with a maximum current efficiency of 3.4 cd·A⁻¹. Further study found that current efficiency and power efficiency of the tandem OLED adding BCP as hole blocking layer (HBL) can achieve 7.85 cd·A⁻¹ and 0.72 lm·W⁻¹, respectively. It is 2.88 times and 1.57 times larger than those of sing-unit devices, and green peak is restrained effectively.