Preparation, electronic structure, and photoluminescent properties of Eu^2＋ activated BaSi2O5 powder phosphors for solid-state lighting

The green-emitting phosphor BaSi2O5 ：Eu^2＋ 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. Eu^2＋-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 Eu^2＋ is 0.05 mol, and that concentration quenching occurs when the Eu^2＋ content is beyond the critical value. The external quantum efficiency of the optimized BaSi2O5 ：Eu^2＋ 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.