Light Guide Layer Thickness Optimization for Enhancement of the Light Extraction Efficiency of Ultraviolet Light–Emitting Diodes

Abstract

Consider material machinability and lattice mismatch sapphire as substrates for the ultraviolet-C light-emitting diodes (UV-C LEDs) are commonly used, but their high refractive index can result in the total internal reflection (TIR) of light whereby some light is absorbed, therefore caused reducing light extraction efficiency (LEE). In this study, we propose a method to optimize the thickness of a sapphire substrate light guide layer through first-order optical design which used the optical simulation software Ansys SPEOS to simulate and evaluate the light extraction efficiency. AlGaN UV-C LEDs wafers with a light guide layer thickness of 150–700 μm were used. The simulation proceeded under a center wavelength of 275 nm to determine the optimal thickness design of the light guide layer. Finally, the experimental results demonstrated that the initial light guide layer thickness of 150 μm the reference output power of 13.53 mW, and an increased thickness of 600 um resulted in output power of 20.58 mW. The LEE can be increased by 1.52 times through light guide layer thickness optimization. We propose a method to optimize the thickness of a sapphire substrate light guide layer through first-order optical design. AlGaN UV-C LEDs wafers with a light guide layer thickness of 150–700 μm were used. Finally, the experimental results demonstrated that the LEE can be increased by 1.52 times through light guide layer thickness optimization.

Enhancement of Light Extraction Efficiency of UVC-LED by SiO2 Antireflective Film

“…In the past few decades, AlGaN-based ultraviolet light-emitting diode (UV-LED) has been attracting extensive attention due to its applications in water sterilization, surface disinfection, and biological detection, thanks to its compactness, long-term reliability, and being free of contamination [1][2][3][4][5][6]. With the outbreak of the coronavirus epidemic in 2019 (COVID-19) [7,8], more researchers joined the development of highly efficient UVC-LED, since it is promising for virus disinfection [7][8][9][10]. However, until now, UVC-LED still suffered low quantum efficiencies and weak optical output power.…”

Highly Reflective Thin-Film Optimization for Full-Angle Micro-LEDs

“…Several researchers have also considered various LED substrate designs to change the light field patterns. Lai et al used a sulfuric acid wet etching process to form a triangular pyramid pattern on c-plane sapphire substrates to achieve higher light extraction efficiencies and increase the light angles; Lan et al proposed a patterned sapphire substrate (PSS) combined with packaged inverted trapezoidal flip-chip micro-LEDs that show strong peaks and large light angles; Zhang et al studied flip-chip deep-ultraviolet LEDs with nano-patterned sapphire substrate (NPSS) structures to show that the NPSS structure can achieve wide angles and enhance light extraction efficiency [39][40][41]. Optical components have also been added to optical modules to modulate the light distributions.…”