Iridium(iii) phosphors with bis(diphenylphorothioyl)amide ligand for efficient green and sky-blue OLEDs with EQE of nearly 28%

In this study, a new ligand, bis(diphenylphorothioyl)amide (Stpip), containing phosphorus-sulfur (P?S) bonds was synthesized as an ancillary ligand. Four iridium(iii) complexes (Ir(ppy)(2)(Stpip), Ir(tfppy)(2)(Stpip), Ir(ttppy)(2)(Stpip) and Ir(tntppy)(2)(Stpip) with phenylpyridine derivates (ppy = 2-phenylpyridine); tfppy = 2-[4-(trifluoromethyl)phenyl]pyridine; ttppy = 2-[3,5-bis(trifluoromethyl)phenyl]pyridine; tntppy = 2-[2,6-bis(trifluoromethyl)-4-pyridyl]pyridine) as the main ligands were investigated. Due to the stable S-Ir bonds, these complexes emitted green or sky-blue photoluminescence with high quantum yields (Ir(ppy)(2)(Stpip): (max) = 490 nm, phi = 44.7%; Ir(tfppy)(2)(Stpip): (max) = 495 nm, phi = 85.4%; Ir(ttppy)(2)(Stpip): (max) = 477 nm, phi = 92.1%; Ir(tntppy)(2)(Stpip): (max) = 516 nm, phi = 90.8%) and good thermal stability. Using these compounds as emitters, all organic light-emitting devices (OLEDs) showed satisfactory performances. Notably, the device with the Ir(tfppy)(2)(Stpip) emitter achieved a maximum luminance of 37 321 cd cm(-2) as well as maximum current efficiency, power efficiency and external quantum efficiency of 61.7 cd A(-1), 48.5 lm W-1 and 21.8%, respectively. Moreover, the device with the Ir(ttppy)(2)(Stpip) complex exhibited the highest EQE value of nearly 28%. These results showed that bis(diphenylphorothioyl)amide is a promising ancillary ligand for efficient phosphorescent Ir(iii) complexes and OLEDs.