THESIS
2014
xiv, [86] pages : illustrations ; 30 cm
Abstract
GaN-based light emitting diode (LED) is a very hot topic these years for their diverse
applications, such as liquid crystal displays’ backlighting, vehicle lamps and both indoors
and outdoors illumination. However, the wall plug efficiency of GaN-based LEDs is still
not high enough; the heat produced by the chip will gradually degrade the chip’s
efficiency as well as life span. And the light extraction efficiency is limited by total
internal reflection inside the chip, originated from the large refractive indices difference
between GaN and air.
Photonic crystals (PHCs) have the ability to control and couple the trapped light and
enhance the light extraction efficiency of LED. But the poor interaction between PHCs
and low order modes becomes the bottleneck for further extraction...[
Read more ]
GaN-based light emitting diode (LED) is a very hot topic these years for their diverse
applications, such as liquid crystal displays’ backlighting, vehicle lamps and both indoors
and outdoors illumination. However, the wall plug efficiency of GaN-based LEDs is still
not high enough; the heat produced by the chip will gradually degrade the chip’s
efficiency as well as life span. And the light extraction efficiency is limited by total
internal reflection inside the chip, originated from the large refractive indices difference
between GaN and air.
Photonic crystals (PHCs) have the ability to control and couple the trapped light and
enhance the light extraction efficiency of LED. But the poor interaction between PHCs
and low order modes becomes the bottleneck for further extraction efficiency
improvement. The p-GaN surface PHCs on patterned sapphire substrate (PSS) LED
structure is proposed for the first time and shows its potential by combining PSS’s
scattering effect and PHCs diffractive capability to extract these low order modes.
The p-GaN surface PHCs on PSS LED has an 18% wall plug efficiency and exhibits
4.3-5.5% higher radiometric power as compared to the conventional PSS LED. Moreover
the extraction efficiency improvement is even as high as 14%.
Post a Comment