Red Phosphors for Solid State Lighting Applications

Solid state lighting with gallium nitride (GaN) light emitting diodes (LEDs) will be the next generation of white LEDs. The numerous advantages of LEDs over incandescent bulbs and florescent lamps include lower energy consumption and a longer life. In addition, LEDs do not contain the mercury found in compact fluorescent bulbs. The next generation white LEDs contain a GaN chip emitting light at 400 nm with red, green and blue phosphors.

The purpose of my research is to create a red phosphor capable of excitation at 400 nm where the LED outputs are maximized. I will investigate the effects of adding salt fluxes and dopants, such as bismuth, to change particle morphology and tune the excitation. I use a flux method to synthesize the red phosphor, yttrium oxysulfide doped with europium (Y 2O 2S:Eu). The systems to be studied include alkali-metal phosphates. The addition of bismuth is known to shift the excitation to longer wavelengths. I plan to synthesize phosphors with different amounts of Bi 3+ and see its effect. I will also try to tune the particle morphology by varying the salt fluxes as well as the other reaction parameters.

The synthesized phosphors are analyzed by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy.