Elaborate Design of d⁸–d¹⁰ Heteronuclear Phosphors for Ultrahigh-Efficiency Solution-Processed Organic Light-Emitting Diodes

Highly soluble d⁸–d¹⁰ heteronuclear phosphors afford an alternative approach to achieve high-efficiency organic light-emitting diodes (OLEDs) through a solution process. In this work, four highly phosphorescent d⁸–d¹⁰ heteronuclear complexes with significant Pt–Au interactions were prepared. By judicious selection of sterically hindered and π-conjugated substituents in triphosphine ligands, the phosphorescence is dramatically promoted through effectively prohibiting nonradiative thermal relaxation with an efficiency of 0.94–0.99 in doping films. Exploiting highly emissive Pt–Au complexes as phosphorescent dopants, ultrahigh-efficiency solution-processed OLEDs were attained. The peak current efficiency, power efficiency, and external quantum efficiency are 96.2 cd A^–1, 65.0 lm W^–1, and 26.4% for the green-emitting PtAu₂ phosphor and 68.6 cd A^–1, 42.5 lm W^–1, and 25.1% for the orange-emitting Pt₂Au phosphor, which represent the state-of-art for solution-processed OLEDs based on non-iridium phosphors.