Enhancement of Light Extraction Efficiency in GaN-Based Blue Light-Emitting Diodes by Doping TiO₂ Nanoparticles in Specific Region of Encapsulation Silicone

Abstract

TiO2 nanoparticles (NPs) are doped in silicone for encapsulation of GaN-based blue light-emitting diodes (LEDs). The average refractive index of silicone is increased by doping TiO2 NPs with an average diameter of 21 nm, and the light extraction efficiency of GaN-based blue LEDs is also increased. Four different TiO2 NPs doping profiles are evaluated including without TiO2 NPs doping, uniform doping, doping around the LED chip only, and doping in the region far from the LED chip. LED, with TiO2 NPs (weight percentage of 0.01%) doping around the LED chip only, has the highest luminous flux of 0.98 lm at 20 mA. The conventional blue LED without TiO2 doping has the luminous flux of 0.94 lm at 20 mA. According to our calculations based on the experimental results, the enhancement of the luminous flux is 3 and 5% higher than that without TiO2 doping packages at 20 and 80 mA, respectively. TiO2 doped in silicone can not only increase the luminous flux but also inhibit the lumen degradation under the stress test for 1500 h.

A Review of Moldflow and Finite Element Analysis Simulation of Chip Scale Packaging (CSP) for Light Emitting Diode (LED)

“…Fillers such as silica are added into the silicone system to improve the mechanical properties such as reducing CTE, improve toughness, elongation, tear and thermal conductivity [27]. Other optical functional substances such as TiO2 nanoparticles are doped into the silicone to encapsulate GaN-based LEDs to increase the refractive index and improve the light extraction efficiency of LEDs [27,28].…”

Reliability testing in GaN-based blue light-emitting diodes by doping TiO2nanoparticles into silicone encapsulation

“…7) All these solutions have one significant purpose in common, that is, to reduce internal reflection and improve the escape cone, as well as light extraction of GaN-based LEDs during the fabrication of LED chips. In many studies, LEDs with TiO 2 -coated phosphors, 8) nanopatterns, 9) highrefractive-index TiO 2 nanoparticles (NPs), 10,11) and gradedrefractive-index coatings 12) have been utilized to achieve a high light extraction efficiency in the LED packaging process.…”