Efficient organic light-emitting diodes with narrow emission bandwidths based on iridium(iii) complexes with a pyrido[3′,2′:4,5]pyrrolo[3,2,1-jk]carbazole unit

Abstract

In order to realize efficient organic light-emitting diodes (OLEDs) with good color-purity, iridium(III) (Ir(III)) emitters with high luminous efficiency and narrow full width at half maxima (FWHM) are required. In this work, two main ligands incorporating a pyrido[3′,2′:4,5]pyrrolo[3,2,1-jk]carbazole unit with a rigid structure to realize carrier recombination balance and restrict intramolecular relaxation were developed. Four Ir(III) complexes with isomers peaking at 500 and 551 nm exhibit short phosphorescence lifetimes lower than 1 μs, high photoluminescence quantum yields of up to 89% and narrow FWHMs of 37 nm. Moreover, the devices based on two of the complexes with better thermal stability (>400 °C) show high external quantum efficiencies (EQE_max) of 23.8% and 24.5%, respectively, with efficiency roll-offs of less than 5%. Particularly, the electroluminescence FWHM bandwidth of one device is only 30 nm, which was rarely reported for Ir(III) complex-based OLEDs. Therefore, the strategy for main ligands with rigid structures provides an innovative method for realizing efficient Ir(III) complex-based OLEDs with narrow emissions.