Warm white light and colour tunable characteristics of Dy3+ co-doped with Eu3+ and Pr3+ zinc sodium bismuth borate glasses for solid state lighting applications

Present work reports the colour tunable characteristics of Dy3+- doped zinc sodium bismuth borate glasses with Eu3+ and Pr3+ co-dopants synthesized through melt quench technique. The absence of sharp peaks in the XRD confirmed the amorphous nature of co-doped glasses. Absorption peaks of Dy3+, Eu3+ and Pr3+ions are found in visible and NIR region of the spectrum. The optical band gap of the glasses were determined through absorption spectra. The excitation spectra exhibited various transitions of Dy3+, Eu3+ and Pr3+ ions in the UV and blue region of the spectrum. The emission spectra of Eu3+ and Pr3+co-doped glass showed blue, yellow and red emissions. Decay curves were measured to confirm the energy transfer processes between Dy3+→Eu3+ and Pr3+ ions. The Inokuti-Hirayama model was used to understand the nature of interaction between Dy3+→Eu3+ and Pr3+ ions during non-radiative energy transfer in the co-doped glasses. CIE chromaticity coordinates shifted from yellowish to orange-reddish region. The correlated colour temperature value of optimum glass was around 3800 K which further illustrates the application of co-doped glasses in indoor lighting under UV/blue light excitation.