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

Abstract

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 Φ_PL= 88±2 % and Φ_PL= 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 (η_EL) were observed, indicating enhancement of electron injection and transport (electron current) in these emitting layers