Highly efficient platinum(ii) complexes overcoming Pt–Pt interactions and their applications in organic light-emitting diodes

Abstract

Phosphorescent Pt(II) complexes have garnered considerable attention owing to their high photoluminescence quantum efficiencies (PLQEs), tunable emission colors, larger Stokes shifts, and high electrochemical stability. However, in thin-film and solid state, Pt–Pt interactions occur between planar Pt(II) complexes due to their close proximity, resulting in undesired spectral alterations. Here, we synthesized three novel Pt(II) complexes by incorporating methyl substituent acetylacetone with large steric hindrance as an auxiliary ligand. The strategic inclusion of steric hindrance and precise ligand alignments effectively overcame Pt–Pt interactions. This tailored design approach ensures nearly identical photoluminescence spectra in solid or thin-films and solutions, coupled with significantly enhanced PLQEs approaching 100% in solid or thin-films. Moreover, utilizing one of the Pt(II) complexes as an emitter in non-doped and doped devices achieved the outstanding maximum external quantum efficiency of 19.6% and 25.2%, respectively. Our research has advanced the exploration of Pt(II) complexes with a large steric hindrance ligand, highlighting their promising potential as emitters in electroluminescent devices.