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

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 Pr 3+ 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 (YPO 4 :Bi 3+ ) 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 YPO 4 , 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 Bi 3+ ions can trap thermalized electrons. This work highlights the key role of Bi 3+ 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.