Ionic Multi-Resonant Thermally Activated Delayed Fluorescence Emitters for Light Emitting Electrochemical Cells

We designed and synthesized two new ionic thermally activated delayed fluorescent (TADF) emitters that are charged analogues of a known multiresonant TADF (MR-TADF) compound, DiKTa. The emission of the charged derivatives is red-shifted compared to the parent com-pound. For instance, DiKTa-OBuIm emits in the green (λPL = 499 nm, 1 wt% in mCP) while DiKTa-DPA-OBuIm emits in the red (λPL = 577 nm, 1 wt% in mCP). In 1 wt% mCP films, both emitters showed good photoluminescence quantum yields of 71% and 61%, and delayed life-times of 316.6 μs and 241.7 μs, respectively, for DiKTa-OBuIm and DiKTa-DPA-OBuIm, leading to reverse intersystem crossing rates of 2.85 × 103 s-1 and 3.04 × 103 s-1. Light-emitting electrochemical cells were prepared using both DiKTa-OBuIm and DiKTa-DPA-OBuIm as ac-tive emitters showing green (λmax = 534 nm) and red (λmax = 656 nm) emission, respectively.