Influences on LED Optical Characteristics When Varying ZnS Particle Sizes Impacting Scattering Coefficients

Abstract

This study investigates the influence of zinc sulfide (ZnS) particle size variation on the optical and colorimetric performance of white light-emitting diodes (LEDs), with particular attention to parameters including luminous flux, correlated color temperature (CCT), color rendering index (CRI), and color quality scale (CQS). ZnS, a high-refractive-index scattering medium, was selected as a secondary phosphor encapsulant to modulate photon transport within the LED package. Mie scattering theory, implemented through MATLAB-based numerical simulations, was employed to systematically evaluate the optical behavior of LEDs incorporating ZnS particles of various diameters. By modeling scattering efficiency, angular light distribution, and chromatic response, the study quantitatively assesses the trade-offs between luminous efficacy and color fidelity. The simulation results reveal that increasing ZnS particle size enhances light scattering and spatial uniformity but leads to a reduction in overall luminous output and an increase in CCT deviation. Larger particles also result in a modest decrease in CRI and CQS values, indicating partial spectral distortion due to excessive backscattering. These findings highlight the critical role of particle size optimization in achieving balanced optical performance, where medium-sized ZnS particles provide the best compromise between color accuracy and luminous efficiency. The outcomes of this work offer valuable design insights for developing high-quality, color-stable, and energy-efficient white LEDs suitable for both general illumination and specialized optical applications.