Gold(I) Multi-Resonance Thermally Activated Delayed Fluorescent Emitters for Highly Efficient Ultrapure-Green Organic Light-Emitting Diodes

Acceleration of singlet-triplet intersystem crossings (ISC) is instrumental in bolstering triplet exciton harvesting of multi-resonance thermally activated delayed fluorescent (MR-TADF) emitters. This work describes a simple gold(I) coordination strategy to enhance the spin-orbit coupling of green and blue BN(O)-based MR-TADF emitters, which results in a notable increase in rate constants of the spectroscopically observed ISC process to 3x10(9) s(-1) with nearly unitary ISC quantum yields. Accordingly, the resultant thermally-stable Au-I emitters attained large values of delayed fluorescence radiative rate constant up to 1.3x10(5)/1.7x10(5) s(-1) in THF/PMMA film while preserving narrowband emissions (FWHM=30-37 nm) and high emission quantum yields (ca. 0.9). The vapor-deposited ultrapure-green OLEDs fabricated with these Au-I emitters delivered high luminance of up to 2.53x10(5) cd m(-2) as well as external quantum efficiencies of up to 30.3 % with roll-offs as low as 0.8 % and long device lifetimes (LT60) of 1210 h at 1000 cd m(-2).

Automated summary

This study improves the triplet exciton harvesting efficiency of thermally activated delayed fluorescent materials through a coordination strategy using metal-organic compounds, resulting in higher emission rates and quantum yields. Additionally, the fabricated ultrapure-green OLEDs exhibit high brightness and external quantum efficiencies, as well as low roll-offs and long device lifetimes.