White Light Generation in Dy³⁺-Doped Sodium Lead Alumino Borosilicate Glasses for W-LED Applications

Abstract

Excitation and emission spectra of sodium lead alumino borosilicate glass doped with different concentrations of Dy³⁺ have been reported. The concentration of Dy³⁺ were varied from 0.5 to 1.5 mol%. As a result of 385 nm excitation wavelength, the luminescence spectra showed three characteristic bands at 482 nm and 575 nm and 665 nm. These absorption bands were attributed to ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2 transitions respectively of Dy³⁺ ions. ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2 transitions respectively of Dy³⁺ ions. The yellow to blue intensity ratio increases (1.063 to 1.093) with increase in Dy³⁺ ion concentration. The decay rates exhibit single exponential for lower concentrations and turns into non exponential for higher concentrations. The non-exponential nature of the decay rates is well-fitted to the Inokuti-Hirayama model for S = 6, which indicates that the nature of the energy transfer between donor and acceptor ions is of dipole-dipole type. The lifetime for the ⁴F_9/2 level of Dy³⁺ ion decreases (0.634 to 0.580 ms). The chromaticity coordinates have been calculated from the emission spectra and analyzed with Commission International de I’Eclairage diagram. The chromaticity coordinates visible in the white light region for all concentrations of Dy³⁺ ions in the present glasses. The correlated color temperature value varies from 5107 to 5362 K (closer to the day light value of 5500 K). These results indicate that Dy³⁺-doped sodium lead alumino borosilicate glasses can be development of white light emitting diodes and suitability for solid state lasers applications.