A practical degradation based method to predict long-term moisture incursion and colour change in high power LEDs

Law, T. K. and Lim, F. (2018) A practical degradation based method to predict long-term moisture incursion and colour change in high power LEDs. IEEE Photonics Journal, 10(5), 8201414. (doi: 10.1109/JPHOT.2018.2869726)

Abstract

The effect of relative humidity on LEDs and how the moisture incursion is associated to the color shift is studied. This paper proposes a different approach to describe the lumen degradation of LEDs due to the long-term effects of humidity. Using the lumen degradation data of different types of LEDs under varying conditions of relative humidity, a humidity based degradation model (HBDM) is developed. A practical estimation method from the degradation behaviour is proposed to quantitatively gauge the effect of moisture incursion by means of a humidity index. This index demonstrates a high correlation with the color shift indicated by the LED's yellow to blue output intensity ratio. Physical analyses of the LEDs provide a qualitative validation of the model, which provides good accuracy with longer periods of moisture exposure. The results demonstrate that the HBDM is an effective indicator to predict the extent of the long-term impact of humidity and associated relative color shift.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Law, Thong Kok and Lim, Dr Fannon
• Authors: Law, T. K., and Lim, F.
• College/School: College of Science and Engineering; College of Science and Engineering > School of Engineering
• Journal Name: IEEE Photonics Journal
• Publisher: Institute of Electrical and Electronics Engineers
• ISSN: 1943-0647
• ISSN (Online): 1943-0655
• Copyright Holders: Copyright © 2018 IEEE
• First Published: IEEE Photonics Journal 10(5):8201414
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher