Thiazole-based metallophosphors of iridium with balanced carrier injection/transporting features and their two-colour WOLEDs fabricated by both vacuum deposition and solution processing-vacuum deposition hybrid strategy

Abstract

New phosphorescent iridium(III) cyclometallated complexes bearing thiazole-based ligands (IrTZ1 and IrTZ2) have been developed. The functionalized organic ligands derived by combining the thiazolyl moiety and triphenylamino group have conferred not only favorable hole-injection/hole-transporting (HI/HT) features but also more balanced charge carrier injection/transporting traits to the as-prepared iridium(III) metallophosphors. Owing to the unique electronic structures afforded by the ligand, the orange organic light-emitting devices (OLEDs) made from IrTZ1 can furnish peak external quantum efficiency (ηext) of 14.82%, luminance efficiency (ηL) of 39.97 cd A−1 and power efficiency (ηp) of 34.95 lm W−1. Inspired by its outstanding electroluminescence (EL) performance, the orange IrTZ1 phosphor complemented with a blue phosphor FIrpic was employed to fabricate highly efficient white organic light-emitting devices (WOLEDs) with a single emission layer. Despite their simple device configuration, the optimized WOLEDs can still maintain decent electroluminescence (EL) ability with ηext of 7.20%, ηL of 18.07 cd A−1 and ηp of 19.57 lm W−1. With the aim to simplify the fabrication process of multi-layered WOLEDs, two-component WOLEDs were obtained through a novel solution processing–vacuum deposition hybrid method with the doped blue fluorescent emission layer deposited by a solution process and the orange phosphorescent emission layer made by vacuum deposition. The WOLEDs prepared using such exploratory approach can show an attractive EL performance with ηext of 9.06%, ηL of 22.72 cd A−1 and ηp of 17.28 lm W−1. All these data have indicated not only the great potential of the orange phosphor in monochromatic and white OLEDs, but also the importance of the hybrid method for simplifying WOLED fabrication.