Trap-Engineered LiCaBO3:Pr3+ Phosphor for Solar-Blind Ultraviolet Luminescence and Reversible Photochromism

Multifunctional phosphors that integrate background-free ultraviolet-C (UVC) persistent luminescence with rewritable optical memory are highly desirable for smart photonic applications. However, achieving such systems remains challenging, as it requires the integration of long-lived carrier storage and reversible photochromic switching within a single defect landscape. Here, we report a single-activator multifunctional phosphor, LiCaBO 3 :Pr 3+ (LCBO:Pr), which couples multi-responsive UVC luminescence with reversible photochromism. Under 248 nm excitation, LCBO:Pr exhibits intense UVC down-shifting emission (276 nm). Remarkably, the same Pr 3+ centers also enable anti-Stokes UVC emission under 450 nm excitation, allowing blue-light-driven UVC output. Beyond X-ray-excited radioluminescence, LCBO:Pr demonstrates efficient energy storage and releases dual-channel UVC/red persistent luminescence (>24 h) after excitation ceases. This process is accompanied by a reversible white-to-brown photochromic transition with a high coloration degree of 61.2%, which can be nearly completely erased by heating or blue-light bleaching, achieving recovery efficiencies of 98.7% and 97.1%, respectively. Experimental analyses and first-principles calculations reveal that defect states associated with V O3 and B i govern both carrier trapping and color-center formation. The coupling of these defect-mediated processes enables integrated optical functionalities within a single material platform, allowing multichannel information writing, readout, and erasure, and offering a versatile platform for solar-blind photonic applications.