Phosphor-In-Glass (PiG) Composites for Thermally Stable W-LEDs: Fabrication and Properties

The current work describes the fabrication and property evaluation of white light emitting Ce3+: Y3Al5O12 (YAG) reinforced glass composites, i.e., phosphor-in-glass (PiG) composites with varying YAG concentrations. At first, a few silicate glasses were prepared and optimized to have low softening temperatures and a refractive index close to the YAG phosphor. The PiG composite pellets were fabricated with different concentrations of phosphor by weight i.e. 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75% and 2% followed by sintering of the green pellets at the softening temperature (530 °C) of the base glass. The prepared PiG composites were characterized for temperature dependent photoluminescence up to 175 °C and chromaticity at ambient temperature. Under the excitation of the blue laser source of 460 nm wavelength, the composites exhibit white light emission with acceptable color rendering index (CRI) values ranging from 71 to 80, while the correlated color temperature (CCT) ranges from 5472 to 4859 K. The thermal stability of the 2% PiG pellet was compared with that of the phosphor-in-resin taken from commercially available white LED. The temperature-dependent photoluminescence (PL) up to 175 °C depicts that the PiG composite retained 90% of the room temperature intensity. In contrast, the phosphor-in-resin (PiER) was found to retain only 70% of the room temperature PL intensity. This indicates PiG is thermally stable over PiER and can be considered an excellent candidate for replacing commercially used PiER composite for LED applications.