Super‐Wideband‐Responsive Photon Conversion Covered From X‐Ray to Near Infrared in Y ₂ Mo ₄ O ₁₅ : Er/Tm Near‐Infrared Luminescent Materials

ABSTRACT Near‐infrared‐III (NIR‐III) phosphors possessing both super‐wideband spectral response and efficient photon conversion capabilities are exceptionally scarce compared to their NIR‐I/II counterparts. Herein, a novel Y 2 Mo 4 O 15 : Er/Tm phosphor with large ion spacing, low lattice symmetry, and relatively narrow bandgap is proposed. Under super‐wideband excitation covered from x‐ray to NIR, the NIR‐III downshifting luminescence (DSL) of Tm 3+ ions is significantly enhanced, which is attributed to the nearly 95% efficient energy transfer from Er 3+ to Tm 3+ . Specifically, under x‐ray, ultraviolet (UV: λ ex = 365 nm), and visible (Vis: λ ex = 450 nm) light excitation, the Y 2 Mo 4 O 15 : Er/Tm phosphor exhibits Tm 3+ emission intensities that are 1.94, 2.93, and 2.84 times higher than those under direct excitation of Tm 3+ , respectively. Notably, a highly sensitive and non‐invasive fluorescence relative‐intensity concentration analysis system was developed based on the distinct of NIR‐III spectral responses to different functional groups, achieving a detection limit of 0.0968 vol% and a goodness‐of‐fit of 0.9938. This study not only introduces a high‐performance NIR‐III luminescent material but also provides crucial theoretical insights and novel design strategies for advanced lanthanide‐doped phosphors.