A Polymer Featuring Thermally Activated Delayed Fluorescence as Emitter in Light-Emitting Electrochemical Cells.

Semiconducting polymers that feature thermally activated delayed fluorescence (TADF) can deliver a much-desired combination of high-efficiency and metal-free electroluminescence and cost-efficient solution-based fabrication. A TADF-polymer is thus a very good fit for the emitting compound in light-emitting electrochemical cells (LECs), since the commonly employed air-stabile and few-layer LEC architecture is well suited for such solution-based fabrication. Herein, we report on the first LEC device based on a TADF-polymer as the emitting species, which delivers a luminance of 96 cd m-2 at 4 V and a current efficacy of 1.4 cd A-1 and >600 cd m-2 at 6 V, which is competitive with the performance of multilayer organic light-emitting diodes based on the same TADF-polymer. We further utilize the established sensitivity of the emission of the TADF-polymer to its environment to draw conclusions on the exciton populations in host-guest and host-free TADF-LEC devices.