Broadband photoluminescence toward the NIR II region and stable green ceramic pigments based on a novel NaBaScSi2O7:xCr silicate phosphor

Cr3+-activated near-infrared (NIR) phosphors are the most promising materials for commercialization. However, the emission of most Cr3+-activated phosphors is typically located in the NIR-I region and achieving luminescence towards the NIR-II region (>900 nm) via Cr3+ doping remains challenging. This study reports a novel Cr3+-activated NaBaScSi2O7 phosphor that exhibits broadband NIR emission centred at 974 nm with a full width at half maximum of 140 nm under 493 nm blue light excitation. The emission wavelength exceeds that of most Cr3+-activated NIR phosphors. The underlying mechanism for the encouraging phenomenon is attributed to the strong charge polarisation arising from the intrinsic local coordination environment of the Cr3+ ions, as confirmed by charge differential density (CDD) and the electron localization function (ELF) analyses. The photoluminescence properties of phosphors were systematically investigated, and the performance of the fabricated NIR pc-LED device was evaluated for night vision and non-invasive imaging. Notably, the NaBaScSi2O7 phosphor displayed a bright green colour with excellent colour properties and its potential as a stable green ceramic pigment was explored.