Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Multi-Azimuth Failure Mechanisms in Phosphor-Coated White LEDs by Current Aging Stresses

Zhangbao Peng
ORCID logo ,
Ziquan Guo
,
Tingzhu Wu
ORCID logo ,
Peng Zhuang
,
Yuan Shi
,
Tien-Mo Shih
,
Yijun Lu
,
Hao-Chung Kuo
* ,
Zhong Chen
*
Version 1 : Received: 14 March 2018 / Approved: 15 March 2018 / Online: 15 March 2018 (16:32:48 CET)

A peer-reviewed article of this Preprint also exists.

Peng, Z.; Guo, Z.; Wu, T.; Zhuang, P.; Ye, Z.; Shi, Y.; Shih, T.-M.; Lu, Y.; Kuo, H.-C.; Chen, Z. Multi-Azimuth Failure Mechanisms in Phosphor-Coated White LEDs by Current Aging Stresses. Appl. Sci. 2018, 8, 610. Peng, Z.; Guo, Z.; Wu, T.; Zhuang, P.; Ye, Z.; Shi, Y.; Shih, T.-M.; Lu, Y.; Kuo, H.-C.; Chen, Z. Multi-Azimuth Failure Mechanisms in Phosphor-Coated White LEDs by Current Aging Stresses. Appl. Sci. 2018, 8, 610.

Abstract

We have experimentally analyzed multi-azimuth degradation mechanisms that govern failures of commercially-available high-power (1 Watt) phosphor-coated white (hppc-W) light-emitting diodes (LEDs) covered with peanut-shaped lens under three current-stress aging (CSA) conditions. Comprehensive analyses focus on photometric, chromatic, electrical, thermal, and packaging characteristics. At the packaging level, (a) the decrease of the phosphor-conversion efficiency, (b) the yellow-browning of the optical lens, and (c) the darkening of the silver-coated reflective layer deposited with extraneous chemical elements (e.g., C, O, Si, Mg, and Cu, respectively) contribute collectively to the integral degradation of the optical power. By contrast, Ohmic contacts, thermal properties, and angles of maximum intensity remain unchanged after 3840 h aging in three cases. Particularly at the chip level, the formation of point defects increases the number of non-radiative recombination centers, and thus decreases the optical power during aging stages. Nevertheless, in view of the change of the ideality factor, the dopant activation and the annealing effect facilitate the increase of the optical power in two specific aging stages (192 h∼384 h and 768 h∼1536 h), respectively. This work offers a systematic guidance for the development of reliable LED-based light sources in general-lighting areas.

Keywords

light-emitting diodes; failure mechanisms; current-stress aging; reliability

Subject

Engineering, Electrical and Electronic Engineering

Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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