High fluorescence efficiency of dual-wavelength white OLED with NPB emission and triplet annihilation

Abstract A high-efficiency fluorescent dual-wavelength white organic light-emitting diode (WOLED) was fabricated with a single emission layer (EML) comprising ITO/MoO3/NPB/Spiro-Pye:DCJTB/Bphen/LiF/Al. OLEDs with a 2 nm-thick MoO3 showed a 6% decrease in the operating voltage and a 14% increase in the external quantum efficiency (EQE). The NPB emission that occurred near the NPB/EML interface was investigated with a carrier blocking layer containing Ir(ppy)3 and Ir(piq)3. Excess electrons in the EML affected the emission of NPB, even at a low voltage of 4 V. The maximum luminescence, current efficiency, and power efficiency of the WOLED were 21,070 cd/m2, 18.09 cd/A, and 8.77 lm/W, respectively. A high EQE of 8.16% was achieved, which exceeded the theoretical limit of 5% for all-fluorescent OLEDs.