The exciton-exciton annihilation rate and the monomolecular recombination rate of excitons govern the dynamics of the population in the reservoir. Here, the ECPL dynamics remain the same across all intensities. While the presence of an intensity-dependent negative ECPL response clearly suggests the presence of a nonlinear loss channel for the population, the dynamics indicate the overall relaxation of the exciton population in the tens of picosecond timescale. This can be rationalized by considering a bimolecular recombination rate, which at these densities manifest in annihilation timescales that are orders of magnitude faster than exciton lifetime, and importantly within the time resolution of the experiment. A more detailed explanation of this can be found in Supporting Information Note 1 and Figure . The observed decay rate of the ECPL is thus a measurement of the component of exciton lifetime within the sub-nanosecond timescale.