Achieving Ultra-Broadband Sunlight-Like Emission in Single-Phase Phosphors: The Interplay of Structure and Luminescence.

The quest for artificial light sources mimicking sunlight has been a long-standing endeavor, particularly for applications in anticounterfeiting, agriculture, and color hue detection. Conventional sunlight simulators are often cost-prohibitive and bulky. Therefore, the development of a series of single-phase phosphors Ca 9 LiMg 1-x Al 2x/3 (PO 4 ) 7 :0.1Eu 2+ (x = 0-0.75) with sunlight-like emission represents a welcome step towards compact and economical light source alternatives. The phosphors are obtained by an original heterovalent substitution method and emit a broad spectrum   spanning from violet to deep red. Notably, the phosphor with x = 0.5 exhibits an impressive full width at half-maximum of 330 nm. A synergistic interplay of experimental investigations and theory unveils the mechanism behind sunlight-like emission due to the local structural perturbations introduced by the heterovalent substitution of Al 3+ for Mg 2+ , leading to a varied distribution of Eu 2+ within the lattice. Subsequent characterization of a series of organic dyes combining absorption spectroscopy with convolutional neural network analysis convincingly demonstrates the potential of this phosphor in portable photodetection devices. Broad-spectrum light source testing empowers the model to precisely differentiate dye patterns. This points to the phosphor being ideal for mimicking sunlight. Beyond this demonstrated application, the phosphor's utility is envisioned in other relevant domains, including visible light communication and smart agriculture.