The Cs4PbBr6 NCs also produce a strong EPR signal upon illumination, but the signal remains intense up to 18 and 12 min in Sol. 1 and 2, respectively. This finding indicates the increased stability of Cs₄PbBr₆ compared to CsPbBr₃, with Cs₄PbBr₆ being three times more stable than the CsPbBr₃ NCs in Sol. 1. Interestingly, in Sol. 2, both the CsPbBr3 and Cs4PbBr6 NCs signal intensity starts to decrease faster than in Sol. 1. This behavior can be attributed to the faster decomposition of HPs in high concentrations of EtOH under the illumination conditions.