Short-Range Coulomb Interaction Is a Key to Switch the Utilization of Higher Triplet Excitons in Multiresonance Thermally Activated Delayed Fluorescence Doped Film

Multiresonance thermally activated delayed fluorescence (MR-TADF) materials have attracted widespread attention due to ultrahigh definition display standards. However, many MR-TADF materials lack TADF properties in both the solution and solid states. Interestingly, the TADF characteristics appear once these MR-TADF compounds are doped in a suitable host film, but the precise mechanism involved in the host-guest interaction remains uncertain. Herein, we systematically investigated the role of host-guest interactions employing doped films (