Gold(I) Multi‐Resonance Thermally Activated Delayed Fluorescent Emitters for Highly Efficient Ultrapure‐Green Organic Light‐Emitting Diodes
Siyuan Cai, Glenna So Ming Tong, Lili Du, Gary Kwok‐Ming So, Faan‐Fung Hung, Tsz‐Lung Lam, Gang Cheng, Hui Xiao, Xiaoyong Chang, Zong‐Xiang Xu, Chi‐Ming Che
Abstract
Abstract 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 3×10 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 1.3×10 5 /1.7×10 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 2.53×10 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 (LT 60 ) of 1210 h at 1000 cd m −2 .