Light can strongly couple with molecules to form polaritons that can significantly alter excited energy states. This paves the way for innovative approaches to developing light based technologies, enhancing energy transfer over long distances, and facilitating the making and breaking of chemical bonds. [1-2] In my talk, I will discuss our recent work examining the impact of strong light-matter coupling on the physics of organic semiconductors and devices. In the first case, I’ll discuss the potential of strong light-matter coupling to reduce excimer emission. Thermally activated delayed fluorescence (TADF) has garnered significant attention due to its capacity to harvest triplet excitons back into bright singlet excitons through reverse intersystem crossing (RISC) using thermal energy. However, in OLEDs, TADF emitters frequently experience molecular aggregation, which limits their applicability because of aggregation-induced excimer formation that results in a larger Stokes shift and broader emission spectrum. We demonstrate that in the strong light matter coupling regime, both prompt and delayed excimer emission can be suppressed, and an increase in RISC rate constants of up to 33% can be achieved, providing a pathway to harvest non-radiative triplets more efficiently. (3) In the second case, I will discuss the longer effective charge carrier lifetimes observed in OSCs operating under strong light-matter coupling, which we reveal result from reduced bimolecular recombination. [4] This study underscores the significant impact of strong light-matter coupling on modifying the device physics in OSCs, paving the way for engineering more efficient OSCs.