Fluorine‐Compensation Strategy to Prepare Lead‐Free Double Perovskite‐Embedded Composite Ceramics for Laser‐Driven Lighting With High CRI

ABSTRACT Laser‐driven lighting demands robust color converters with broad, continuous spectra to achieve high‐fidelity illumination, yet conventional phosphors often suffer from spectral deficiencies that lower the color rendering index (CRI) and cause visual discomfort. To address this, we develop CaF 2 ‐Cs 2 Na 0.7 Ag 0.3 In 0.97 Bi 0.03 Cl 6 composite phosphor ceramics (CPCs) utilizing spark plasma sintering at temperatures below 490°C. A fluoride‐mediated defect compensation mechanism, in which F − ions migrate from the CaF 2 matrix into Cl − vacancies of the double perovskite, simultaneously facilitates full densification and passivates non‐radiative recombination centers. This dual effect enables the CPCs to emit warm white light with a full width at half maximum of 224 nm and a near‐unity relative photoluminescence quantum yield. The CPCs also exhibit superior stability against heat, moisture, and laser irradiation, together with a high thermal conductivity of 9.4 W·m − 1 ·K − 1 at 25°C. A prototype laser‐driven lighting device based on these CPCs delivers high‐quality warm white light with a CRI (R a ) of 96. This work establishes a fluoride‐compensation low‐temperature sintering strategy for robust lead‐free double perovskite‐embedded CPCs with broadband emission, targeting high‐fidelity laser‐driven lighting.