Pore characteristics for improving luminous efficacy of phosphor-in-glass

Pores formed during the sintering of a glass/phosphor mixture affect the scattering and path of light within the resulting phosphor-in-glass (PIG) plate. An investigation of the interactions between blue light from an LED chip and pores within a PIG plate is therefore needed to understand the effect of light scattering on the optical properties. To this end, various glass compositions based on SiO₂-B₂O₃-ZnO were prepared so as to better understand the effect of modifiers (i.e., Li₂O, Na₂O, La₂O₃, WO₃) on the viscosity and pore properties at different sintering temperatures. This study found that PIGs sintered within a given viscosity range exhibit different optical properties depending on their pore size and overall porosity; a higher luminous efficacy observed in the case of intermediate scattering length values was due to an improved interaction between pores and light. This is a significant finding, as ensuring suitable PIG pore characteristics is an important factor in achieving a desired spectrum and high efficacy from white LEDs.