Spectroscopic investigation on thermally stable Dy3+ doped zinc phosphate glasses for white light emitting diodes

Abstract

Optically transparent dysprosium ions doped lead zinc phosphate glasses have been prepared via melt quenching technique to study the luminescent properties and their applications for white light emitting diodes (w-LEDs). X-ray diffraction (XRD) pattern confirmed the amorphous nature of the as-prepared glass. The glass transition temperature (Tg) and thermal stability (ΔT) were determined by using Differential Scanning Calorimetry (DSC). The vibrational features were characterized by Raman and FT-IR, which indicate the presence of poly-phosphate structure dominated by Q2 and Q1 structural units. The intense emission bands observed at 482 nm (blue) and 574 nm (yellow), where the yellow to blue intensity ratio for all excitation wavelengths (NUV to blue range) were found to lie in the vicinity of unity, yielding to intense white light emission. The evaluated CIE chromaticity coordinates (0.309, 0.341) for the optimized glass (GP10) at 350 nm excitation fall in the pure white region, which is in proximity with commercial w-LED (Blue LED + YAG:Ce3+) and NTSC system for white light emission. The correlated color temperature (CCT) of the optimized glass is 6547 K, which represents cool white light emission. The decay profiles have been measured for the excited 4F9/2 level and analyzed.