Meaning
Supporting platforms or plates that allow light to pass through them but scatter it so that objects behind are not clearly visible are used in specific optoelectronic applications. The deployment of translucent substrates balances the need for light transmission with the requirement for diffuse illumination in displays, solar cells and light-emitting diodes. These substrates are typically made of polycrystalline ceramics, textured glasses or polymer composites that contain light-scattering centers.
Their optical properties are governed by the grain size, porosity and composition of the material.
Optical Transmission
Diffusion of the transmitted light wave occurs as it encounters internal boundaries or particles with different refractive indices. In translucent substrates, the total hemispherical transmission can be high, while the regular inline transmission remains low due to this diffuse scattering. This scattering is a function of the wavelength of the light and the size of the scattering centers, with shorter wavelengths being scattered more strongly.
Scattering Source
Microstructural features such as residual pores, grain boundaries in non-cubic ceramics and second-phase precipitates act as the primary scatterers. Minimizing these features can transition translucent substrates into transparent ones, but this requires more complex and expensive processing steps. For many applications, a controlled level of translucency is preferred to maximize light extraction or to provide uniform illumination without hotspots.
Operational Requirement
Implementing these materials in production lines requires robust optical characterization to ensure consistent scattering and transmission across different production batches. If the transmission of translucent substrates varies too much between lots, the optical performance of the assembled devices will be inconsistent. The cost of calling a supplier’s pilot batch acceptable without verifying these properties is the rejection of the final assembled displays, which increases material costs.
Utilizing spectrophotometry with integrating spheres during the incoming inspection phase verifies that the optical scattering meets the design specifications before the assembly process.
