OPTIMISATION OF THE SPECTRAL COMPOSITION OF LED SOURCES OF ‘WHITE’LIGHT BASED ON BLUE LEDs WITH LIGHT-CONVERTING COATING OF ONE /TWO COMPONENT PHOSPHORS: CALCULATION METHODOLOGY AND MODELLING RESULTS

The article considers the ways to reasonably assess the possibilities of creating modern light-emitting diodes (LEDs) with specified spectral parameters by using single- and multi-component phosphors. The main goal of the study was to develop a methodology for modelling the spectral composition of a white light source based on blue LEDs and one- or two-component phosphors to determine the compliance of their spectral parameters with a reference source of ‘white’ light, depending on the contribution of the excitation source radiation. To model the spectral composition of LEDs, we developed software using the Python LuxPy package. This made it possible to obtain comprehensive information about the spectral parameters of the synthesised light, including the correlated colour temperature (CCT), colour rendering index, light quality scale (CQS), colour accuracy index (IES Rf) and saturation index (IES Rg). It was found that in order to obtain white light with high quality indicators, it is necessary to optimise the spectral composition of the radiation by choosing the optimal ratio of blue LEDs and phosphor. Experimental measurements of the emission spectra of phosphors based on yttrium-aluminium (YAG) and gallium-gadolinium (GGG) garnets activated with cerium allowed to determine the ranges of CCT values for white LEDs based on them. It was found that LEDs with CCT in the range from 4701 K to 6439 K can be created on the basis of YAG phosphor, while GGG phosphor allows to obtain CCT in the range from 2972 K to 3294 K. The use of a two-component phosphor (50% YAG and 50% GGG) allows to create LEDs with CCT in the range from 3563 K to 4210 K. The Ra value for LEDs using these phosphors ranges from 73 to 87 units, the CQS value from 75 to 79, the IES Rf value from 78 to 82, and the IES Rg value from 90 to 95. Based on all the phosphors considered, white LEDs with colour rendering parameters that meet the requirements for both outdoor and, in most cases, indoor lighting can be manufactured.