Efficient red phosphorescent Ir(iii) complexes based on rigid ligands with high external quantum efficiency and low efficiency roll-off. Issue 18 (7th April 2020)

• Record Type: Journal Article
• Authors: Liu, Sheng-Nan; Tong, Kai-Ning; Zhao, Yue; Cheng, Jin-Feng; Fung, Man-Keung; Fan, Jian
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 18(2020)
• Page Start: 6168
• Page End: 6175
• Publication Date: 2020-04-07
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9tc06940b
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Two highly efficient red phosphorescent Ir(iii ) complexes were prepared by the introduction of rigid cyclometalating ligands. Abstract : The rigid ligands in red phosphorescent Ir(iii ) complexes can suppress the vibration and rotation around metal ions to maximize the utilization of low energy singlet and triplet states, thus greatly reducing the probability of non-radiative decay. In this paper, the coordination groups (phenyl and quinolinyl) are fused by a cyclohexyl group to produce rigidified ligands (5, 6-dihydro-benzo[ c ]acridine and 9-fluoro-5, 6-dihydro-benzo[ c ]acridine). A bulky ancillary ligand (2, 2, 6, 6-tetramethylheptane-3, 5-dione) was applied for the synthesis of Ir(iii ) complexes (Ir-DHBA and Ir-F-DHBA ) to minimize the intimate interactions between Ir(iii ) molecules and consequently to reduce triplet–triplet annihilation and triplet-polaron annihilation. When the two Ir(iii ) complexes were applied as dopants in organic light-emitting diode (OLED) devices, they both showed excellent electroluminescence (EL) performance. The device based on Ir-DHBA demonstrated a low efficiency roll-off with a maximum external quantum efficiency (EQE) of 26.0%, 25.3% EQE at a brightness of 1000 cd m −2 and 22.7% EQE at 10 000 cd m −2 . The device based on Ir-F-DHBA (at a doping ratio of 3%) with an exciplex as a co-host showed a maximum EQE of over 28% with Commission Internationale de l'Eclairage (CIE) coordinates of (0.61, 0.39) and an EL emission peak at 600 nm.