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.