Non‐Rare‐Earth UVC Persistent Phosphors Enabled by Bismuth Doping

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Long persistent phosphors (LPPs) have drawn tremendous research interest owing to their mysterious optical phenomena and widespread applications. LPPs in the ultraviolet‐C (UVC, 200–280 nm) spectral range particularly hold promise in terms of sterilization, drug release, and cancer therapy. However, all reported UVC LPPs have so far relied on the use of Pr3+ as the emitter, resulting in a limited scope of such phosphors. Here, a new concept for designing UVC LPPs is proposed, leading to the birth of the first non‐rare‐earth phosphor (YPO4:Bi3+) with a UVC afterglow duration of more than 2 h. Experimental characterizations including thermoluminescence spectra and high‐resolution synchrotron X‐ray diffraction, coupled with first‐principles calculations, reveal that various intrinsic defects in YPO4, such as Y vacancies and Y–O vacancy complexes, serve as hole traps to capture and store a large number of holes created by X‐ray irradiation, while Bi3+ ions can trap thermalized electrons. This work highlights the key role of Bi3+ ions in mediating energy storage and release in persistent phosphors by acting as both electron traps and emitters, and thus offers new opportunities for rationally designing non‐RE‐activated UVC LPPs.