Deep-red organic light-emitting diodes with stable electroluminescent spectra based on zinc complex host material

Abstract

A zinc complex host material named Zn(PPI)₂ (PPI = 2-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenol) is synthesized by an improved strategy. Combined with dopant Ir(piq)₃ and Ir(pmiq)₂(acac), deep-red phosphorescent organic light-emitting diodes are fabricated and investigated. The devices show a highest external quantum efficiency of 9.5% based on Ir(piq)₃ and 13.1% for Ir(pmiq)₂(acac). All these devices show very stable electroluminescent spectra without significant shift during current density increase. Commission Internationale de l'Eclairage coordinates of (0.68, 0.32) and (0.70, 0.30) are obtained respectively.