EFFECT OF THE SIZE DISTRIBUTION OF YGAG:Ce-BASE POWDER PHOSPHOR ON WHITE LED PARAMETERS

Abstract

One of the most critical parameters in the production of white LEDs, along with efficiency, includes phosphor consumption. Little attention has been given in the literature to the relationship between the efficiency of white LEDs and the particle size and morphology of yttrium – gallium – aluminium garnet-base powder phosphors or to the consumption of phosphor for the production of light-emitting sources and how it tends to change. The problem of bringing down production costs due to production process optimization and luminescence enhancement is extremely important when it comes to the fabrication of white LEDs. This paper examines the relationship between the efficiency of white LEDs and the particle size and morphology of yttrium – gallium – aluminium garnet-base powder phosphors. It also shows how the consumption of phosphor changes when making light-emitting sources. The authors looked at the particle size distribution, morphology, X-ray phase composition, as well as spectral parameters. It was found that the luminous intensity of powder phosphors is considerably changing as the particles get smaller and that the particle size distribution of phosphor has only a slight effect on the luminous intensity of light-emitting diodes (LEDs). Using experimental data, the authors demonstrate a reduction in the consumption of powder phosphor and, consequently, the fact of saved cost for preparing the phosphor mixture for making white LEDs. The following regularity was established upon analysis of luminescence spectra of powder phosphors: the luminous intensity of powder phosphors tends to consistently decrease as the size of phosphor particles get smaller. The analysis of LED test results revealed that the luminous efficacy of the LED module stays at approximately the same level in the range of 135 to 140 lm/W, at various particle size distribution parameters of green phosphor. An optimum size distribution of phosphor has been defined that would ensure high LED efficacy at low consumption of powder phosphor. The contributors to this research study include O. M. Chapura, Lead Engineer at the Research Laboratory for Thin Films and Nanoheterostructures, Lab Complex of Clean Zones, Faculty of Physics and Technology at the NorthCaucasus Federal University.