Improving intramolecular rates and suppressing intermolecular annihilation processes in OLEDs with strong and weak light-matter coupling: from experiment to theory

TADF and phosphorescence emitters overcome the spin-statistics bottlenecks by efficiently converting triplets to photons. However, phosphorescence and reverse intersystem crossing (RISC) rates are microseconds-slow, leading in unwanted exciton collisions when OLEDs are operated at high current density. Polaritons, hybrid light-matter states that rise when the energy exchange rate between a material and its environment surpasses their intrinsic losses, offer a platform for modifying intramolecular rates and intermolecular interactions, making them favorable for OLEDs. In this talk, I will revisit our experiments on polariton OLEDs for the hypothesis of inducing RISC in fluorescent emitters (10.1515/nanoph-2023-0587), and go beyond this by presenting our recent theoretical model for polaritonic OLED processes not restricted to the single-excitation subspace (10.1002/adom.202403046). This allowed us, for the first time, to explore RISC together with triplet-triplet and singlet-singlet annihilation (TTA and SSA). In addition, we analyze the effect of the number of molecules and f molecules and study how SSA could be reduced with strong coupling.