Enhancing the Efficiency of Polariton OLEDs in and Beyond the Single‐Excitation Subspace

Abstract Organic light‐emitting diodes (OLEDs) have redefined lighting with their environment‐friendliness and flexibility. However, only 25% of the electronic states of organic molecules can emit light upon electrical excitation, limiting the overall efficiency of OLEDs. Strong light–matter coupling, achieved by confining light within OLEDs using mirrors, creates hybrid light‐matter states known as polaritons, which could “activate” the remaining 75% electronic triplet states. Here, triplet‐to‐polariton transition is studied and rates for both reverse inter‐system crossing and triplet‐triplet annihilation are derived. In addition, how the harmful singlet‐singlet annihilation could be reduced with strong coupling is explored.