Achieving BT.2020 red emission with narrowband deep-red iridium complexes in OLEDs

Abstract

Achieving deep-red emission that meets the stringent BT.2020 color standard remains a critical challenge for phosphorescent organic light-emitting diodes (OLEDs). Here, we report two newly designed Iridium (Ir) (III) complexes, Ir(6-PhIqXy)2dend and Ir(7-PhIqXy)2dend, which incorporate a 1-(3,5-dimethylphenyl)-phenyl-isoquinoline ligand to enhance electron density, extend It-conjugation, and promote a planar molecular geometry favorable for horizontal dipole orientation. The newly designed Ir(III)-based emitters exhibit high photo-luminescent quantum yields of 79.1% and 80.1%, deep-red emission peaks at 635 and 637 nm, and narrow full widths at half maximum (FWHMs) of 47 and 50 nm, respectively. Furthermore, the introduction of the ligand results in a high horizontal dipole ratio of 90.7% for Ir(6-PhIqXy)2dend, leading to efficient light outcoupling and a maximum external quantum efficiency (EQE) of 19.1% without spectral broadening. Importantly, OLEDs incorporating both emitters exhibit ultra-narrowband deep-red emission peaking at 641 nm with a FWHM of 49 nm, yielding Commission Internationale de l'Eclairage (CIE) coordinates of (0.705, 0.294), which is the closest match to the BT.2020 red standard (0.708, 0.292) reported to date among Ir(III)-or Platinum(II)-based OLEDs. This work demonstrates that rational ligand engineering in Ir(III)-based phosphorescent emitters can concurrently achieve BT.2020-level color purity and high efficiency, providing a promising strategy for next-generation ultra-high-definition OLED displays.