Rational design and synthesis of orange emissive Ir(III) complexes Bearing Coumarin 6 and Imidazo-Diazaphene for Solution-Processed OLEDs

Abstract

Organic light emitting diodes (OLEDs) have found extensive application in solid-state lighting and display technologies owing to their advantages of high energy efficiency, environmental friendliness, lightweight design, and flexibility. The phosphorescent iridium(III) complexes are widely used in the emissive layer of OLEDs due to their wide range of emission colors, short phosphorescent lifetime, and good photostability. Currently, the majority of OLEDs utilizing iridium(III) complexes are fabricated through the vacuum thermal evaporation technique. In contrast, this solution method offers the advantages of simplified preparation and minimal material consumption. In this paper, coumarin 6 was selected as the main ligand owing to its advantages of simple synthesis, high yield, and excellent luminescence stability. Two ionic phosphorescent iridium(III) complexes (Ir-TPIP/Ir-TPHIP) were synthesized by introducing triphenylamine moiety into imidazo[4,5-f][1,10]o-diazaphene and accessing a hexane chain at the imidazole as the two auxiliary ligands, respectively, both Ir-TPIP and Ir-TPHIP exhibit orange light with the maximum emission wavelengths of 564 and 585 nm in solution, respectively. Subsequently, Ir-TPIP/Ir-TPHIP-based orange OLEDs were prepared by the solution method, and the maximum brightness of the devices were 3038/1045cd/m², with corresponding maximum CEs, PEs, and EQEs values of 4.13/4.45 cd/A, 0.79/0.87 lm/W and 1.81/1.87 %, respectively.