Red and Near Infrared Emissive Bis-Tridentate Ir(III) Phosphors for Organic Light Emitting Diodes

Efficient saturated red and near-infrared (NIR) emissive materials are needed in the development of organic light-emitting diodes (OLEDs), with applications extending beyond flat panel displays and lighting luminaries. Toward this aim, a series of bis-tridentate Ir(III) complexes (3a ‒ 3c and 4a ‒ 4c) are designed and synthesized, showing emission spanning the region of 601‒694 nm in degassed toluene. Their emission tuning is mainly achieved using monoanionic chromophoric chelates, L1H for red and L2H for deep-red and NIR, where the extended π-conjugation and electron deficient N atoms are introduced synergistically. Moreover, three ancillary chelates, X1H₂, X2H₂, and X3H₂, delivered a secondary influence via varied donor strength to the central Ir(III) atom. The resulting red and deep-red OLED devices exhibit maximum (max.) external quantum efficiencies (EQEs) of 21.4% and 18.1% with peak maximum at 620 and 666 nm, respectively. More impressively, the device based on 4b delivers a NIR emission peak maximum at 702 nm with a maximum EQE of 10.0%. © 2023 Wiley-VCH GmbH.