A simple sol-gel approach was used to fabricate orthorhombic Er³⁺-doped BaSrGd₄O₈ nano-crystals with space group Pnma. The orthorhombic phase and the crystallinity of the prepared samples were confirmed by Powder X-ray diffraction (PXRD) and the Rietveld refinement technique. The non-uniformity of particles between 35 nm and 60 nm sizes was observed by morphological probes via scanning and transmission electron microscopies. PL spec-troscopy was utilised to determine decay lifetime, radiative conversions, rate of radiation-less transitions, and numerous intensity constraints. PL intensity reached a maximum of 5.0 mol%, and above that, it started to decrease owing to con-centration quenching. The internal quantum efficacy of the optimal sample was 81.2%. The bandgap of the optimal sample was found to be lower than that of the pure host lattice, which proves the best luminance of the doped nanophosphor. The CIE and CCT coordinates are in the greenish part of the chromaticity diagram. The optimal sample may be used for solid-state lightings, pc-WLEDs, lasers, sensors, and advanced solar cells.

Nanophosphor, Green Light, Quantum Efficiency, WLEDs