Tunable white light in trivalent europium single doped tin fluorophosphates ultra-low melting glass

Abstract

In recent years, low melting temperature glasses have received wide attention as the hosts of phosphor-converted light emitting diodes (pc-WLED). In this work, a series of trivalent europium doped tin fluorophosphates glasses were prepared by conventional melting method. Under ultraviolet excitation, the blue-green broadband emission from Sn2+ activation centers in the glass matrix and the red emission of Eu3+ ions together constituted a cool white luminescence. The spectra analysis was used to demonstrate the energy transfer between Sn2+ centers and Eu3+ ions. The results showed that Sn2+ and Eu3+ possessed independent intrinsic emission and mutual energy transfer simultaneously. The 5D4 and 5G2 excited states of Eu3+ ion favored the energy transfer to Sn2+ center, the 5L6 excited state of Eu3+ ion would absorb more of the energy by the Sn2+ ground state excitation to contribute on red emission. Therefore, the fluorescent glass can transform cool white light to warm white light by changing the excitation wavelength. The tunable white light is obtained in the WLED devices built with the glass and commercial UV chips.