Fabrication and characterization of YAG:Ce phosphor films for white LED applications

YAG:Ce (or Y₃Al₅O₁₂:Ce³⁺) based phosphor films have been widely used in phosphor converted white LED along with InGaN based LED to generate white light for lighting applications. The properties of the phosphor films were determined by the properties of the phosphor and silicone matrix as well as their interaction. Morphological, structural, optical properties of phosphor powder and phosphor films were carried out in the paper. This work also investigated a quantitative relationship between the properties and compositions of the films that were made from YAG:Ce phosphor and silicone. A mathematical model was also proposed to describe the relationship between the optical properties of the phosphor/silicone composite films and their compositions when the incident light was from blue LED chips. The simulated spectrum based on the mathematical model was found in good agreement with the one measured experimentally. The transmittance of the phosphor films gradually decreased as phosphor concentration in the film increased. Furthermore, the luminous efficacy of all the phosphor films were higher than the pure LED light. The uniform bright white light could be obtained by packaging the 40 wt% YAG:Ce phosphor film with InGaN LED chips.