A previous report has attributed the sub-band gap feature below 1 ps to bandgap renormalization. Based on this assumption, we compare the band gap renormalization energy of both NC samples by calculating the energy difference between the GSB and the sub-band gap ESA as indicated in Figure . Although slightly varying at different times, we consistently find higher renormalization energies between 3 -15 % for the exchanged NCs (99 meV after 600 fs) compared to the native system (89 meV after 600 fs). These findings can be interpreted as evidence for stronger excitonic behavior and quantum confinement in the DCzGPC-exchanged NCs (Fig. + Table ). 35 With regard to the large chemical instability of perovskites, we perform stability tests in solution monitored by PL intensity changes upon water addition (Fig. ). For the native NCs and the DCzGPC passivation alike, we find the previously observed initial increase in PL, assigned to the passivation of surface defects. However, this gain diminishes after 10 min without stirring the solution, which we attribute to the beginning water-mediated decomposition of the NCs. For the DCzGPC-exchanged NCs, this deterioration is significantly slowed down after 40 min, indicating a greater robustness against water. The stability of the particles exchanged with DCzGPC in polar solvents, such as THF or ethyl acetate, for at least two months without a significant loss in luminosity further supports their robustness.