Preparation, electronic structure, and photoluminescent properties of Eu²⁺ activated BaSi₂O₅ powder phosphors for solid-state lighting

The green-emitting phosphor BaSi₂O₅:Eu²⁺ was synthesized by the conventional solid state reaction. Using the CASTEP code, BaSi₂O₅ is calculated to be an intermediate band gap semiconductor with an indirect energy gap of about 3. 2 eV. As expected, the calculated optical band gap of BaSi₂O₅ is lower compared to the experimentally determined values. Eu²⁺-activated BaSi₂O₅ phosphor can be excited efficiently over a broad spectral range between 200 and 400 nm, and has an emission peak at 500 nm with a full width at half maximum of 95 nm. The study of concentration-dependent emission intensity shows the optimal concentration of the Eu²⁺ is 0.05 mol, and that concentration quenching occurs when the Eu²⁺ content is beyond the critical value. The external quantum efficiency of the optimized BaSi₂O₅:Eu²⁺ is 96. 1%, 70. 2% and 62. 1% under excitation at 315, 350 and 365 nm, respectively. The superior optical properties of the sample show the potential as an ultraviolet converting green-emitting phosphor for white light emitting diodes. (paper)