Study of phosphor layer structure for improving the luminous efficiency of white LEDs

Abstract

In recent years, lighting emitting diodes (LEDs) is one of the lighting research directions attracting wide attention from scientists and manufacturers because of its outstanding advantages compared to traditional lighting sources. LED is a technology with great advantages such as energy savings, environmental friendliness, and compactness. However, LED lights haven’t reached the level of physical illumination such as lighting efficiency, color quality, an affordable cost compared to conventional light. Motivated by this unfulfilled potential, I propose solutions to improve the luminous efficiency and color quality.

In this thesis, the theoretical concept of LED-diodes function and connected concepts such as optical performance, lighting efficiency, structure of phosphor are described. Physical modeling aspects, as well as currently relevant applications of white LEDs are examined in detail. On that basis, the optimal phosphor structures, and the novel materials for the white LEDs are proposed to enhance their performance towards higher luminous flux, better brilliant color rendering index, longer life-span, and lower production cost. Furthermore, to optimize the white LEDs, the location of phosphor, the distance of phosphor layers, various phosphor materials, their optimal scattering, thickness, concentration, and particle size are investigated as a tool for manufacturers to diversify the portfolio of potential materials. In addition to that, the optical performance of LEDs packages such as scattering intensity, luminous flux, color uniformity, and color rendering index are also analyzed following the Mie-scattering theory criterion. The simulations in MatLab – Simulink and Light Tools software are used to verify the optical performance of the proposed methods