This study investigates the dynamics of self-hybridized exciton-polaritons (E–Ps) in two-dimensional (2D) halide perovskites. Excitons, bound electron-hole pairs, can form E–Ps when confined in an optical cavity. In 2D halide perovskites, self-hybridized E–Ps can form at specific crystal thicknesses, leading to multiple E–P modes with high Q factors. These E–Ps modulate optical dispersion, enhancing sub-gap absorption and emission. Energy transfer from higher energy E–Ps to lower energy E–Ps was confirmed through ultrafast measurements. Additionally, E–Ps were shown to facilitate charge transport at interfaces. The study demonstrates that 2D halide perovskites can support multiple E–P branches in an open cavity, with each branch altering the relaxation pathway of E–Ps. The research also shows that sub-bandgap polariton states can be electrically harvested, opening new possibilities for polaritonic devices. The findings provide insights into charge and energy transfer in E–Ps, with potential applications in polaritonic photodetectors and photovoltaics. The study used various techniques, including photoluminescence spectroscopy, temperature-dependent PL, PL mapping, and time-resolved PL measurements, to investigate the optical properties of E–Ps. The results confirm that E–Ps can modify the optical dispersion of 2D perovskite layers, enabling sub-gap absorption and emission. The study also demonstrates that energy transfer occurs between E–P branches, and that sub-bandgap photons can be harvested due to modified optical dispersion. The research highlights the potential of 2D halide perovskites for strong light-matter coupling and their application in energy harvesting and photonic devices.This study investigates the dynamics of self-hybridized exciton-polaritons (E–Ps) in two-dimensional (2D) halide perovskites. Excitons, bound electron-hole pairs, can form E–Ps when confined in an optical cavity. In 2D halide perovskites, self-hybridized E–Ps can form at specific crystal thicknesses, leading to multiple E–P modes with high Q factors. These E–Ps modulate optical dispersion, enhancing sub-gap absorption and emission. Energy transfer from higher energy E–Ps to lower energy E–Ps was confirmed through ultrafast measurements. Additionally, E–Ps were shown to facilitate charge transport at interfaces. The study demonstrates that 2D halide perovskites can support multiple E–P branches in an open cavity, with each branch altering the relaxation pathway of E–Ps. The research also shows that sub-bandgap polariton states can be electrically harvested, opening new possibilities for polaritonic devices. The findings provide insights into charge and energy transfer in E–Ps, with potential applications in polaritonic photodetectors and photovoltaics. The study used various techniques, including photoluminescence spectroscopy, temperature-dependent PL, PL mapping, and time-resolved PL measurements, to investigate the optical properties of E–Ps. The results confirm that E–Ps can modify the optical dispersion of 2D perovskite layers, enabling sub-gap absorption and emission. The study also demonstrates that energy transfer occurs between E–P branches, and that sub-bandgap photons can be harvested due to modified optical dispersion. The research highlights the potential of 2D halide perovskites for strong light-matter coupling and their application in energy harvesting and photonic devices.