Abstract Deep-blue phosphorescent OLEDs (Ph-OLEDs) with high efficiency and stability are essential for advanced display technologies, ensuring sharp image quality and enhanced visibility. In this work, we report a novel class of asymmetric 3 + 2 + 1 coordinated iridium (III) complexes incorporate strongly electron-withdrawing trifluoromethyl (–CF 3) and fluorine (–F) modified N-heterocyclic carbene ligands. This strategic molecular design enables efficient deep-blue emission. Among these complexes, the CF 3 -substituted Ir (III) complex (CF 3 -2) exhibits pronounced charge-transfer (CT) characteristics and a significantly enhanced radiative decay rate (kₑ k r = 1. 28 ×10⁶ s -1), enabling rapid and efficient phosphorescence at 443 nm. Devices employing CF 3 -2 demonstrated exceptional maximum external quantum efficiency (EQE max) of up to 29. 0%, with emission centered at 443 nm and Commission Internationale de L’Éclairage (CIE) coordinates of (0. 147, 0. 089), fulfilling National Television System Committee (NTSC) blue standards for high-quality displays. Meanwhile, devices employing CF 3 -1 reached an EQE max of 24. 6% with a maximum luminance of 6542 cd m −2 and CIE x, y of (0. 152, 0. 126), demonstrating high color purity and efficiency. A control device fabricated without sensitization using CF 3 -1 further confirms its intrinsic material stability by exhibiting a remarkable operational lifetime of LT 50 of 3875 h at L = 100 cd m −2 with CIE x, y of (0. 132, 0. 131). Furthermore, hyper-OLEDs were developed using these complexes as phosphorescent sensitizers. The hyper-OLED incorporating CF 3 -1 with the TADF emitter v -DABNA achieved an impressive device lifetime of LT 50 = 2127 h at 100 cd m −2. In parallel, the CF 3 -2 -sensitized hyper-OLED using DOB2-DABNA-A achieved a deep-blue emission with CIE coordinates of (0. 146, 0. 067) and a lifetime of LT 50 = 373 h under the same luminance, representing a significant advancement in the practical stability of deep-blue OLEDs. Notably, we demonstrate the successful integration of these deep-blue Ph-OLEDs with OLED-on-TFT microdisplay technology, achieving a pixel resolution of 94 PPI (270 × 270 μm) with programmable emission patterns. This innovative molecular coordination design strategy provides valuable insights into ligand engineering and exciton management, opening new pathways toward high-efficiency, long-lifetime deep-blue OLEDs for next-generation microdisplay and display technologies.
Li et al. (Tue,) studied this question.