Iridium(III) Blue Phosphors with Heteroleptic Carbene Cyclometalates: Isomerization, Emission Tuning, and OLED Fabrications

• Published in: Angewandte Chemie International Edition Vol. 64; no. 11; pp. e202421664 - n/a
• Main Authors: Wu, Yixin, Huang, Manli, Cheng, Lin, Zhang, Junyao, Pan, Yi, Yiu, Shek‐Man, Chung Lau, Kai, Yan, Jie, Yang, Chuluo, Chi, Yun
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 10.03.2025; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: blue light emission; Carbenes; Chelates; Chemistry; Chemistry, Multidisciplinary; Energy transfer; Fabrication; Förster resonance energy transfer; High temperature; Iridium; Isomerization; organic light emitting diodes; Phosphors; Photoluminescence; Photons; Physical Sciences; Quantum efficiency; Science & Technology; Substitutes; iridium; LIGHT-EMITTING-DIODES; organic light emitting diodes; COMPLEXES; METAL; blue light emission; LIGAND; F & ouml;rster resonance energy transfer; EFFICIENCY ROLL-OFF; HYPERPHOSPHORESCENCE; Förster resonance energy transfer
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202421664

Ir(III) complexes are particularly noted for their excellent photophysical properties in giving blue OLED phosphors. In this study, two distinctive carbene pro‐chelates LAH2+ and LBH2+ (or LCH2+) were employed in preparation of heteroleptic Ir(III) complexes, to which LAH2+ bears a cyano substituted benzoimidazolium along with N‐mesityl appendage, while LBH2+ (or LCH2+) carries the symmetrical benzoimidazolium entity. Notably, the reversible equilibration at high temperature was observed for m, f‐ct14 and m, f‐ct15 with a single LA chelate. In contrast, only the mer‐substituted m‐ct16 was obtained upon employing two LA chelates. All Ir(III) complexes exhibited blue photoluminescence (ΦPL ≥ ${\ge }$ 78 %) with short radiative lifetimes (τrad ≤ ${\le }$ 1.05 μs) in solution. The Ph OLED device with m‐ct16 afforded an external quantum efficiency (EQE) of 22.8 % at 5000 cd ⋅ m−2. Moreover, the hyper‐OLED based on m‐ct16 and v‐DABNA exhibited EQE1000 of 32.1 % (EQE recorded at 1000 cd ⋅ m−2) and J90 of 15.0 mA cm−2 (current density at 90 % of max. EQE). Its suppressed efficiency roll‐off (EQE of 32.1 % and 27.7 % at 1000 cd ⋅ m−2 and 10000 cd ⋅ m−2) demonstrated a milestone in fabrication of blue OLED devices. Blue hyper‐OLED devices using the Ir(III) emitter m‐ct16 as the dopant sensitizer at 30 wt % and ν‐DABNA as the terminal emitter at 1 (2) wt % afforded blue emission with a narrowband peak maximum at 471 (472) nm, CIEy of 0.157 (0.149), EQE1000 of 32.1 (28.4) %, and J90 of 15.0 (31.0) mA ⋅ cm−2, setting a new record of Figure of merit (FOM) and showing minimal quenching at high current density.