Strategic pyrimidine functionalization of tetradentate Pt(II) complexes for high-performance deep-blue organic light-emitting diodes

This study addresses the longstanding challenges of efficiency, color purity, and device stability in deep-blue emitting tetradentate Pt(II) complexes for organic light-emitting diodes (OLEDs). A novel complex, Pt3N, is developed by strategically incorporating a pyrimidine-functionalized ligand into BD-02, a known blue-emitting Pt(II) complex. The electron-deficient pyrimidine moiety in Pt3N modulates its frontier molecular orbitals and enhances ligand-to-ligand charge transfer, leading to a high photoluminescence quantum yield of 96 %, short exciton lifetime of 1.33 μs, and narrowband blue emission at 458 nm with a full width at half maximum of 23 nm. Comprehensive structural and photophysical analyses, including X-ray crystallography and theoretical calculations, confirm that the spatially confined electronic transitions and suppressed vibrational relaxation exhibited by Pt3N are due to strong intramolecular steric hindrance. OLEDs incorporating Pt3N as a dopant exhibit excellent performance, particularly when using deuterated mixed-host films, with a maximum external quantum efficiency of ~26.9 %, deep-blue color CIE y coordinates (0.10–0.12), and high device durability. Notably, Pt3N-based OLEDs maintain 95 % of their initial luminescence (1000 cd m⁻²) for 110 h. This work highlights the effectiveness of molecular engineering in tuning radiative decay processes and establishes Pt3N as a promising candidate for next-generation deep-blue OLEDs.