Since the PL measurement indicates the decomposition of the NCs in Sol. 1 and 2, we proceeded to examine the stability of CsPbBr3 and Cs4PbBr6 NCs held in the dark and after the illumination. Note that we have not investigated the stability of CsPbBr3 and Cs4PbBr6 NCs in toluene, as previous reports have consistently shown that the HPs-NCs are stable in toluene. For Sol.