Downshifting analysis of Sm3+/Eu3+ co-doped LiBiAlBSi glasses for red emission element of white LEDs

The Sm3+, Eu3+ single doped, and Sm3+/Eu3+ co-doped lithium bismuth alumino borosilicate (LiBiAlBSi) glasses were prepared by using the melt quenching method and studied photoluminescence (PL) excitation, PL emission, and PL decay to have a better insight into their utility as red emission element for white LEDs. Sm3+ doped LiBiAlBSiSm05 glasses exhibit admirable emission features in the reddish-orange region under n-UV excitation (402 nm). Sm3+/Eu3+ co-doped LiBiAlBSi glasses can be adeptly excited by the blue and n-UV region which is confirmed from the excitation spectrum. In the Sm3+/Eu3+ co-doped LiBiAlBSi glasses, the PL decay lifetime for the Sm3+ emitting level (4G5/2) declines and the energy transfer efficiency increases with an upsurge in Eu3+ ion content, which suggests the energy transfer (ET) process occurs from Sm3+ to Eu3+ ions. The ET process from Sm3+ to Eu3+ ions is also suggested by Dexter's ET method and Reisfeld's approximation by using emission spectra due to non-radiative dipole-dipole (d-d) interaction. The calculated values of CIE chromaticity coordinate for the as-prepared glasses under n-UV excitation shifted from reddish-orange to the red spectral part with the upsurge in Eu3+ concentration. The temperature-dependent PL studies of the optimized LiBiAlBSiSE10 glass revealed its superior thermal stability. All the results obtained finally suggest that, the Sm3+/Eu3+ co-doped LiBiAlBSi glass with 0.5 mol% of Sm3+ ions and 1.0 mol% of Eu3+ ions is a thermally stable candidate to produce intense red color needed to fabricate white LEDs under n-UV and blue excitation through the downshifting process.