Time-resolved spectra (Fig. ) revealed dual phosphorescence emission peaks at 446 and 480 nm. The relative emission intensity at 446 nm gradually increased from 0.3 to 6 ms compared to the emission at 480 nm. This behavior can be attributed to a longer phosphorescence lifetime (Fig. ), suggesting that the emission at 446 nm may arise from a T2 radiative transition, possibly resulting from an additional up-conversion process from the T1 to T2 state. To validate these photophysical processes, we measured temperature-dependent phosphorescence spectra (Fig. ), which exhibited a monotonically blue shift from 504 to 477 nm as the temperature increased from 78 to 298 K. This observation suggests that elevated temperature promotes the endothermic up-conversion process from T1 to T2, with a small ΔETT of 0.2 eV, leading to the emission of anti-Kasha phosphorescence (Supplementary Figs. 26-29). The presence of a rigid polymer matrix facilitates the dual-phosphorescence processes by mitigating the influence of intermolecular interactions between emitters. Additionally, the rigid environment provided by the matrix helps suppress nonradiative decay, thereby stabilizing the higher triplet state of the RTP dendrimers. The phosphorescence properties of HCBPSF in doped PMMA films were investigated. The PL and Ph spectra (Fig. ) of PMMA: 1 wt% HCBPSF film exhibited a positive ΔEST of 0.02 eV, indicating the presence of a stable 3 LE state at various temperatures, as confirmed by structure-resolved spectra (Supplementary Fig. ). The films displayed an ultralong phosphorescence lifetime of 1.16 s, with persistent afterglow emission lasting up to 10 s in 298K. Interestingly, the lifetime of the triplet state excitons remained relatively unchanged across different temperatures. The PMMA matrix effectively restricted the mobility of the alkoxy chains in HCBPSF, thereby protecting triplet excitons from quenching and stabilizing the T1 state, which ultimately resulted in extended triplet state exciton lifetimes, enabling ultralong RTP emission. We also demonstrated a simple information anti-counterfeiting application (Fig. ) employing neat films and doped PMMA films. The number "88" exhibited sky-blue emission under UV light excitation. When the UV light was turned off, the portion of the number "8" written with the neat film disappeared due to its short-lived fluorescence, while the remaining portion exhibited afterglow phosphorescence, transforming into a new number "8" after 10 s. Furthermore, we investigated the transient PL decay of HCBPSF in doped PCL and SBS films (Supplementary Fig. ). The different afterglow emission lifetimes observed in these doped films make them promising candidates for advanced encryption applications utilizing time-gated technology.