Light beam interactions and emission performance in powder phosphor materials: The role of the binder

The light emission performance of powder phosphors, employed in a variety of imaging applications, is affected by their structural (i.e., the particle size and packing) and optical properties (i.e., the wavelength of the light rays and the refractive index of the grains). In the chemical synthesis and the corresponding construction development of phosphor layers, the binder plays crucial role though its contribution to the way that the grains are glued together in a packed spatial distribution. In the present work, the influence of the binder on optical diffusion models was examined by using Mie theory and Monte Carlo simulation. To this aim, phosphor layers were investigated assuming different set-ups of refractive indexes (i.e., four cases of phosphor grains and binder combinations). Results showed that the choice of the binder affects the amount and distribution of light mainly through the: (i) domination of light absorption with respect to light scattering, and (ii) the direction of the light beam when light scattering takes place. It is important to note that by changing the refractive index of the binding material the light spread was not considerably varied through the number of light-grain interactions.