This suggests that, to achieve a macroscopic accumulation of polaritons at the lowest energy state, a similar approach to that used in molecular dye cavities and J-aggregate systems can be applied to 2D perovskite systems. In this context, radiative pumping can be used to directly feed the lower polariton branch at �𝑘𝑘 ∥ ���⃗ � = 0, bypassing the scattering mechanisms required for polaritons to relax in energy along the polariton dispersion . Hence, to achieve a critical concentration of polaritons at �𝑘𝑘 ∥ ���⃗ � = 0 it is fundamental to understand the radiative pumping processes taking place in the 2D perovskite microcavity system.