<p>In this work, Eu³⁺/Tb³⁺ doped and co-doped NaCaPO₄ phosphors were synthesised via the solution combustion route. The X-ray diffraction (XRD), morphological, photoluminescence, energy transfer and I–V characteristics of the NaCaPO₄:Tb³⁺, Eu³⁺ phosphor were examined. The codoped samples exhibited tunable green to orange-red emissions, attributed to Tb³⁺→ Eu³⁺ energy transfer. Energy transfer parameters were calculated, and the underlying mechanisms were thoroughly discussed. In addition, I–V characteristics of blank as well as Eu³⁺ co-doped NaCaPO₄:Tb³⁺ phosphor-coated solar cells were investigated under solar simulator as well as direct sunlight. The findings portray improved performance for the coated cells. This exhaustive study recommends the synthesized phosphors promising for WLED and solar cell applications.</p>