Variance of energy transfer dynamics in Ce3+ sensitized Eu3+ and Tb3+ doped alkali free Ba-Al metaphosphate glass: role of the host matrix

Multivalent Ce/Eu/Tb singly doped along with (Ce-Eu) and (Ce-Tb) dual doped alkali-free Ba-Al metaphosphate glasses are prepared by the melt quenching technique and the results of an investigation of the energy transfer dynamics among dopant ions in this host are reported. The alkali free metaphosphate glass matrix facilitated the in situ formation of divalent europium (Eu2+) due to its reducing nature which played a key role in bringing about a difference in Ce3+ sensitization to Eu3+ and Tb3+ ions respectively. In Eu singly doped glass, a radiative energy transfer has been realized from Eu2+ to Eu3+ ions. Whereas in (Ce3+-Eu3+) co-doped glass series, the presence of cerium promotes oxidation of Eu2+ to Eu3+ with simultaneous reduction of Ce4+ to Ce3+ as the Eu2O3 concentration increases. In case of (Ce3+-Tb3+) co-doped glasses, Tb4+ ion formation with an increase of Tb2O3 content has been seen without any change of the Ce3+ content. All these changes have been interpreted and their impact on the energy transfer dynamics has been thoroughly discussed based on the energy level overlap among the do pant ions. The measured quantum yields (QY) of Eu3+ and Tb3+ ions in singly doped glasses are 78% and 83%, respectively, and compared with other host materials. The effective energy transfer of Ce3+-> Tb3+ in the present host makes it a promising material as a UV to visible frequency downshifter for solar cell applications