Inorganic Phophors for Solid State Lighting

Light emitting diode (LED) based lighting has gained importance due to the high luminous efficacy, good color rendering and energy savings. Blue indium-gallium nitride LEDs can be used in combination with green and red phosphors to produce white light. We have investigated the synthesis of red phosphors that could be excited by the blue LED. We chose the yttrium aluminum garnet system doped with cerium and chromium (YAG:Ce,Cr) for our studies. The strategy involved the absorption of the blue light by the cerium ions and transfer to the chromium ions that emit a deep red color. The method used for the syntheses is the solid state route. We carried out the reactions at different temperatures and in various atmospheres and determined the conditions that were optimal of the synthesis of the pure samples. We have studied the effect of changing the amount of Ce and Cr on the luminescence and characterized the samples by using X-ray diffraction and luminescence spectroscopy. X-ray diffraction was used to check the purity of the samples and the photoluminescence measurement was used to measure the color of emission. We have achieved the quenching of the yellow Ce luminescence and a transfer of the energy to the Cr ions. Further work is underway to improve the efficiency of the system.