Pyridinylphosphorothioate-based blue iridium() complex with double chiral centers for circularly polarized electroluminescence

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 9; no. 15; pp. 5244 - 5249
• Main Authors: Lu, Jun-Jian, Tu, Zhen-Long, Luo, Xu-Feng, Zhang, Yi-Pin, Qu, Zhong-Ze, Liang, Xiao, Wu, Zheng-Guang, Zheng, You-Xuan
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 22.04.2021
• Subjects: Chirality; Circular polarization; Crystallography; Efficiency; Electroluminescence; Electron clouds; Emitters; Enantiomers; Iridium compounds; Organic light emitting diodes; Phosphines; Phosphors; Quantum efficiency
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d1tc00832c

Circularly polarized organic light-emitting diodes (CP-OLEDs) have received considerable attention due to their promising applications in 3D displays. However, up to now, CP-OLEDs using iridium( iii ) phosphors as emissive dopants exhibited low brightness, insufficient efficiency, serious efficiency roll-off, and especially low electroluminescence dissymmetry factors ( g EL ). In this study, a blue Ir( iii ) complex Ir(dfppy) 2 (sdpp) (dfppy is 2-(2,4-difluorophenyl)pyridine, sdpp is pyridinylphosphorothioate) peaking at 466 nm was synthesized, and two pairs of enantiomers containing the λ or δ isomer together with a chiral phosphine center ( R or S ) were separated into λ-Ir(dfppy) 2 ( S -sdpp), δ-Ir(dfppy) 2 ( R -sdpp), λ-Ir(dfppy) 2 ( R -sdpp) and δ-Ir(dfppy) 2 ( S -sdpp), respectively. It is the first example to investigate phosphine chirality in an Ir( iii ) complex, and the electron cloud distribution in the chiral conjugated ancillary ligand and λ/δ chirality of the Ir( iii ) center induced Ir(dfppy) 2 (sdpp) to exhibit decent circularly polarized luminescence (CPL) activities with a dissymmetry factor (| g PL |) around 1.4 × 10 −3 . The OLEDs based on Ir(dfppy) 2 (sdpp) exhibited a maximum external quantum efficiency of 13.8% with mild efficiency roll-off. Notably, the CP-OLEDs based on λ-Ir(dfppy) 2 ( S -sdpp), δ-Ir(dfppy) 2 ( R -sdpp), λ-Ir(dfppy) 2 ( R -sdpp) and δ-Ir(dfppy) 2 ( S -sdpp) showed obvious circularly polarized electroluminescence (CPEL) signals with a g EL of −2.1 × 10 −3 , 2.4 × 10 −3 , −2.1 × 10 −3 and 1.9 × 10 −3 , respectively, thus affording an efficient strategy for the design of chiral blue Ir( iii ) emitters and their CP-OLEDs. A blue Ir( iii ) complex with double chiral centers based on the λ or δ isomer together with a chiral phosphine center ( R or S ) can be separated into four isomers, which can show obvious CPL intensity and CPEL properties.