Blue Organic Electrophosphorescence Diodes using Diarylamino-substituted Heterocyclic Compounds as Host Material

Diarylamino-substituted heterocyclic compounds (DHCs), 2,6-dicarbazolo-1,5-pyridine (PYD2) and 2,4,6-tricarbazolo-1,3,5-pyrimidine (PYM3), possess a high triplet energy level (T1) of T1= 2.93 eV (PYD2) and T1= 2.89 eV (PYM3), respectively, in their solid state films. 6wt%-Iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-N,C2]picolinate (FIrpic):PYD2- and 6wt%- FIrpic:PYM3-doped films showed high photoluminescence (PL) efficiencies of ΦPL= 88±2 % and ΦPL= 80±1 %, indicating near perfect confinement of FIrpic triplet excitons. By increasing the FIrpic concentration in DHC hosts, lower driving voltage and higher external electroluminescence (EL) quantum efficiencies (ηEL) were observed, indicating enhancement of electron injection and transport (electron current) in these emitting layers