Enhancing the Luminescence Efficiency of Blue Phosphorescent Organic Light-Emitting Diodes: Constructing Platinum(II) Complexes with a Functionalized Tetradentate Ligand

Efficient, electrochemically stable blue phosphors are essential for advancing the organic light-emitting diode (OLED) industry. Specifically, the characteristics of these phosphors must be further refined to realize commercially viable OLED devices with high stability, efficiency, and color purity. To that end, a new simple molecular design approach is devised in this study for synthesizing tetradentate-ligand-based Pt(II) complexes exhibiting intense blue emission. Essentially, novel Pt(II) complexes Pt3 and Pt4 are prepared by introducing the tert-butyl and cyano groups to the ligand of previously reported highly stable, efficient Pt(II) complexes for preventing molecular aggregation and regulating the frontier levels, respectively, and then fully characterized. Both complexes display a blue emission band in solution and solid states with remarkably low full-width-at-half-maximum values. Additionally, multilayer phosphorescent OLEDs are fabricated using Pt3 or Pt4 as emitters and SiCzCz/SiTrzCz2 as a mixed-host system. The devices demonstrate outstanding performance parameters, such as higher efficiencies than those of the devices containing the previously reported Pt(II) complexes and good color purity (CIEy ≈ 0.18). These findings suggest that the molecular design approach employed in this study for creating tetradentate-ligand-based Pt(II) blue phosphors is effective and can potentially expedite the commercialization of blue phosphorescent emitters in the OLED industry.