Highly efficient chlorine functionalized blue iridium(iii) phosphors for blue and white phosphorescent organic light-emitting diodes with the external quantum efficiency exceeding 20%

Abstract

The absence of highly efficient and stable blue phosphors is still a bottleneck for the development of high quality monochrome and white phosphorescent organic light-emitting diodes (OLEDs). Here, we propose a chlorine-functionalization strategy for blue phosphors, and a series of aromatic chlorine-based high-efficiency blue iridium(III) phosphors (Ir1–Ir4) containing various ancillary ligands was designed and prepared. These phosphors show intensive blue emissions withPL peaks of 468–476 nm and a high Φ_PL of 0.70–0.85 in dichloromethane. Using these blue phosphors as emitters, the fabricated OLEDs also realize similar blue emissions with the peaks located at 472, 484, 476, and 476 nm for the Ir1–Ir4-based OLEDs, respectively. Moreover, the Ir2- and Ir3-based OLEDs exhibit extremely high EQEs exceeding the theoretical limit, reaching 20.43% and 21.41%, respectively. In addition, the two-color white OLED with Ir3 as the blue emitter also achieves an extremely high device efficiency, having a maximum EQE of up to 20.17%. The excellent blue emission and high device efficiency indicates that the four phosphors have huge potential applications for high performance blue and white phosphorescent OLEDs.