Theory‐Guided Defect Tuning through Topochemical Reactions for Accelerated Discovery of UVC Persistent Phosphors

Abstract Long persistent phosphors (LPPs) have attracted enduring attention owing to their wide applications. However, the discovery of LPPs is thus far largely the results of trial and error. Here, theory‐guided defect tuning through topochemical reactions is demonstrated for accelerated discovery of emerging LPPs. First‐principles calculations are employed to identify the thermodynamic charge‐transition levels of different defect states, which help examine whether the candidate structure is a suitable host for afterglow. Rationally tuning the species and concentrations of defects through topochemical reactions is then illustrated, which leads to discovery of Pr³⁺‐doped LaPO₄ featuring ultraviolet C afterglow with a lasting time of over 2 h. Such a strategy, in conjunction with advanced characterizations including high‐resolution synchrotron X‐ray diffraction, positron annihilation lifetime spectroscopy, and electron spin resonance, suggests a radical‐involved afterglow mechanism. Importantly, it is illustrated that this concept can be extended for the discovery of more LPPs. It is suggested that theory‐guided defect engineering enabled by topochemical reactions can be used as a powerful tool to accelerate discovery of novel LPPs with much clearer afterglow mechanisms, with implications even for the design of other optoelectronic materials.