Personal Solar UV Monitoring based on Photoinduced Electron Transfers in Luminescent Materials

Abstract The spectrally‐selective monitoring of doses of UV and visible light is crucial in numerous applications like photodynamic therapy and personal solar UV detection, due to the specific irradiation impact of light with different wavelengths and doses. Herein an approach to design wavelength‐specific integrating light dosimeters is demonstrated based on photo‐induced redox processes of certain lanthanides in phosphate compounds. Systematic experiments reveal that the reduction process is induced through ligand‐to‐metal charge transfer excitation while the oxidation process is achieved upon excitation of either the involved hole traps or 4f^N‐4f^N‐15d¹ transitions of the created divalent dopants. These processes are rationalized in multi‐electron energy level diagrams for local electron transfer. The dose and wavelength‐dependent redox processes allow for selective UV and visible light dosimetry, and the spectral sensitivity of the dosimeter can be tailored by manipulating the dopant or the host. Particularly, the spectral sensitivity of Ba_2.99Eu_0.01(PO₄)₂ better matches the erythemal action spectrum of human skin than that of currently used benchmark polysulphone dosimeters, making it ideally suitable for personal solar UV radiation monitoring. These findings open the door to designing wavelength‐tunable light dosimeters according to the requirements of envisioned applications and are expected to benefit a wide range of luminescent functional devices.