Preparation, electronic structure, and photoluminescent properties of Eu 2+ activated BaSi 2 O 5 powder phosphors for solid-state lighting

The green-emitting phosphor BaSi 2 O 5 :Eu 2+ was synthesized by the conventional solid state reaction. Using the CASTEP code, BaSi 2 O 5 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 BaSi 2 O 5 is lower compared to the experimentally determined values. Eu 2+ -activated BaSi 2 O 5 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 BaSi 2 O 5 :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.