Rapid fabrication of YAG-Ce phosphor glass composites on borosilicate glass for white light LEDs

Abstract

White light is obtained from converting blue light from an LED source with yellow light emission from phosphor such as YAG-Ce. Phosphors are incorporated in glass or a resin matrix to use with blue LED sources. A novel and a versatile method using a pulsed CO₂ laser is presented which helps in rapid fabrication and reducing complexity of fabrication of phosphor glass composites on glass surface. Mixture of YAG-Ce phosphor and recycled borosilicate glass powder is deposited on borosilicate glass substrate using a settling method. The thickness and composition of the deposited layer can be easily controlled by altering the quantity and weight ratio of the mixture, thus making it easier to control the resultant color temperature of the sample. Localized surface melting of the glass is obtained by irradiating the samples with a pulsed CO₂ laser. This creates an adhesion of the mixture to the substrate surface when cooled while encapsulating phosphor in a glass matrix. Phosphor to glass weight ratio as high as 50% can be easily obtained by this method. Phosphor is not exposed to high temperatures for an elongated period to cause thermal degradation, thus avoiding the need to develop special low melting point glass materials. The effects of different parameters such as composition and temperature are presented. This method allows the use of a CO₂ laser to accomplish multiple functions like fabricating microstructures and polishing in a single step to manipulate the light output.