Narrow‐Bandgap CsPbCl₃:Mn²⁺ Ultralong Persistent Luminescence

Abstract The energy transfer mechanism following carrier de‐trapping in ion‐doped persistent luminescence (PersL) materials has remained poorly understood, mainly due to the absence of observable band‐edge exciton PersL in the host. Here, bright PersL in CsPbCl 3 :Mn 2+ under X‐ray excitation, exhibiting remarkable longevity (>60 min at 200 K), is reported. Significantly, the direct bandgap nature of CsPbCl 3 host enables clear observation of band‐edge emission, offering an unprecedented opportunity to investigate the elusive carrier transfer process from traps to emission centers. The results reveal that the PersL process is temperature‐dependent, primarily governed by a thermally‐assisted tunneling (TAT) mechanism, wherein energy is directly transferred from traps to Mn 2+ centers. Only at cryogenic temperatures (77–120 K) do a minor fraction of electrons from shallow traps contribute weakly to PersL via conduction band release. This work advances the mechanistic understanding of PersL and offers a theoretical foundation for optimizing PersL materials.