Energy transfer studies and neutral to warm white light generation in Dy3+-Sm3+ co-doped bismuth phosphate glasses for lighting applications

series of bismuth phosphate (BiP) glasses activated with 0.5 mol% of Dy3+ and different concentrations (0.1, 0.3, 0.5, 1.0, 1.5 and 2.0 mol%) of Sm(3+ )ions were prepared by melt quenching technique. These are characterized through optical absorption, photoluminescence and decay measurements for spectroscopic investigations. The luminescence spectra have been studied under selected excitation wavelengths to examine the energy transfer mechanism in the present Dy3+-Sm3+ co-doped glass by varying Sm3+ ion concentration. The lifetimes of both F-4(9/2) level of Dy3+ ion and (4)G(5/2 )level of Sm3+ ion of co-doped glasses have obtained and found to be decreased with increase in Sm3+ ion concentration. The emission intensity increased with the increase of Sm3+ ion concentration (upto 1.5 mol%) which confirms the energy transfer process between Dy3+ to Sm3+ ions. The CIE chromaticity co-ordinates (x, y), correlated color temperature (CCT) and color purity (CP) were determined from the emission data. From the CIE, CCT and CP values, it can be concluded that there is a color hue from neutral to warm white light region due to Sm3+ ion concentration and selected excitation wavelength. Hence, the obtained results strongly suggest that the present Dy3+-Sm3+ co-doped bismuth phosphate glasses could be useful for lighting applications.