Pyridocarbene-Based Tetradentate Pt(II) Complexes for Long Device Lifetime over 500 h in Blue Phosphorescent Organic...

Blue phosphorescent organic light-emitting diodes (PhOLEDs) face challenges in achieving high efficiency, color purity, and long device lifetime due to exciton quenching and high energy requirements. In this study, two tetradentate Pt(II) complexes, Pt-impy and Pt-Me-impy, are designed and synthesized by incorporating pyridocarbene in their ligands. Pyridocarbene enhances the electrochemical stability, strengthens triplet metal-to-ligand charge transfer characteristics, and improves the spin-orbit coupling, effectively shortening the exciton lifetime and minimizing the quenching effects. Additionally, the introduction of a methyl group as a conformation manager in Pt-Me-impy further improves the color purity by blue-shifting and narrowing the emission spectrum. As a result, Pt-impy and Pt-Me-impy exhibit external quantum efficiencies of 24.5% and 27.4% at the 3 wt.% doping concentration, respectively. In particular, Pt-impy and Pt-Me-impy doped blue PhOLEDs optimized for stability demonstrate a device lifetime of up to 95% of the initial luminance of 543 and 228 h at 1,000 cd m^-2, which has never been achieved in the blue PhOLEDs. This study demonstrates that the synergistic combination of pyridocarbene and the methyl conformation manager is an effective strategy for improving blue PhOLED performance, enhancing their potential for practical applications.