Narrow Energy Gap between Triplet and Singlet Excited States of Sn2+ in Borate Glass

Transparent inorganic luminescent materials have attracted considerable scientific and industrial attention recently because of their high chemical durability and formability. However, photoluminescence dynamics of ns(2)-type ions in oxide glasses has not been well examined, even though they can exhibit high quantum efficiency. We report on the emission property of Sn2+-doped strontium borate glasses. Photoluminescence dynamics studies show that the peak energy of the emission spectrum changes with time because of site distribution of emission centre in glass. It is also found that the emission decay of the present glass consists of two processes: a faster S-1-S-0 transition and a slower T-1-S-0 relaxation, and also that the energy difference between T-1 and S-1 states was found to be much smaller than that of (Sn, Sr)B6O10 crystals. We emphasize that the narrow energy gap between the S-1 and T-1 states provides the glass phosphor a high quantum efficiency, comparable to commercial crystalline phosphors.