Room temperature synthesis, concentration quenching study and defect formation in β-Ag2MoO4:Dy3+- photoluminescence and positron annihilation spectroscopy

Designing new materials for solid state lighting and understanding the various intricacies involved for designing them such as defects, energy transfer and concentration quenching is very important. Such materials will be highly beneficial in optoelectronics, energy and health industry. In this work, an effort has been taken in that direction by exploring room temperature synthesized Dy3+ doped beta-Ag2MoO4 using simple co-precipitation method under neutral conditions. Pure beta-Ag2MoO4 showed blue - green emission upon shining with UV light. On doping Dy3+ an efficient host-dopant energy transfer takes place. The concentration quenching study revealed non-radiative energy transfer in Dy3+ doped beta-Ag2MoO4 takes place via Dexter mechanism of exchange interaction. Additionally, on doping Dy3+ ions in the beta-Ag2MoO4 a multicolour emission could be observed due to presence of blue, yellow and red bands induced by host sensitized energy transfer. Positron lifetime studies show that the Dy3+ doping creates cation vacancies. Positron lifetimes and asymmetry ratios in PL emission show that Dy3+ stabilizes at Ag+ sites. Photoluminescence Lifetime Spectroscopy revealed non-homogenous distribution of Dy3+ ions and its surroundings differ in terms of their vicinity with respect to defects created due to aliovalent doping. Such complete spectrum of work on concentration quenching study, UV excited photoluminescence, defect spectroscopy, local structure of dopant ion and excited state lifetime indicate that the developed phosphor may potentially be used for solid state phosphor for LED application. Future work will be seeing how the material properties change in going to nanodomain and to make it excitable using f-f band (351 nm). The only demerit of this phosphor is the poor absorption in this region.