Customized Cyan Phosphors for Efficient Full‐Spectrum Illumination and Fingerprint Detection

Traditional lighting methods have environmental and efficiency drawbacks. These methods are gradually being overshadowed by light‐emitting diodes (LEDs) because of their superior color rendering and energy efficiency. In this study, color‐tunable NaBa2(Ba/Sr/Ca)Si2O7F:Eu2+ phosphors are successfully designed by modulating the local crystal field environment through homodominant‐group cation substitution, thereby allowing for a spectral shift from blue to bright cyan. Detailed structural analysis of the samples demonstrated the synthesis of high‐quality solid‐solution materials. A comprehensive examination of the phosphor crystal structure, photoluminescence properties, and fluorescence lifetime reveal that the cyan phosphor possesses a remarkable internal quantum efficiency (IQE = 93%) and low thermal quenching characteristics (I423 K/I303 K = 84%). The results illustrate the critical role of Eu2+‐activated cyan phosphors in reducing the spectral gap to attain a natural white‐light spectrum, which is indispensable for achieving high color fidelity. The practical application of cyan phosphors in the fabrication of high‐performance white LED (WLED) (Ra = 96.8) and fingerprint detection is validated, demonstrating their extensive utility in enhancing visual accuracy and identification. Abandoning the traditional trial‐and‐error method, a cation substitution strategy is employed to modulate the local crystal field of Eu2+ ions and tailor cyan phosphors with high quantum efficiency and thermal stability. This high‐performance cyan phosphor can be used for full‐spectrum illumination and fingerprint detection.