A Study of the Upper Layer for Improvement of the Extraction Efficiency in LED

Abstract

In this paper, we improved the light extraction efficiency by considering an additional upper layer on the top surface of a conventional LED. We simulated the LED's light emission as functions of the thickness and the refractive index of the upper layer, and analyzed how the condition improved the light efficiency. When the refractive index's range was from 1.05 to 1.40, the LED emission increased. For that case, the emission also increased as the thickness increased. We experimentally showed that the light extraction efficiency was improved about 22% by forming the upper layer on the top surface of an LED using material with refractive index 1.30 at 589.3 nm. It is expected that forming the upper layer on an LED can easily improve the extraction efficiency.

Variation of Illumination Performance with Source Size and Tolerance Characteristics of Freeform LED Lenses

“…LED(Light emitting diode) 광원과 광학 부품의 성능 향상 에 힘입어, LED는 정보기기 분야뿐만 아니라 일반 조명 분 야에도 그 활용이 확대되고 있으며, LED의 에너지 절감 효 과와 친환경적인 특성으로 인해 기존 조명 대체에 대한 기대 가 높아지고 있다 [1][2][3] . 그러나 기존 조명용 광원과 달리 LED 광원의 방출 분포는 지향성을 가지므로, 원하는 조명 성능(illumination performance) 을 발휘하기 위해서는 2차 광학 소자(secondary optics)의 사 용이 반드시 필요하다.…”