Bridging the "green gap" of LEDs: Giant light output enhancement and directional control of LEDs via embedded nano-void photonic crystals

Yu Lin Tsai, Che Yu Liu, Chirenjeevi Krishnan, Da Wei Lin, You Chen Chu, Tzu Pei Chen, Tien Lin Shen, Tsung-Sheng Kao, Martin D.B. Charlton, Pei-Chen Yu, Chien-Chung Lin*, Hao-Chung Kuo, Jr Hau He

*Corresponding author for this work

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Green LEDs do not show the same level of performance as their blue and red cousins, greatly hindering the solid-state lighting development, which is the so-called "green gap". In this work, nano-void photonic crystals (NVPCs) were fabricated to embed within the GaN/InGaN green LEDs by using epitaxial lateral overgrowth (ELO) and nano-sphere lithography techniques. The NVPCs act as an efficient scattering back-reflector to outcouple the guided and downward photons, which not only boost the light extraction efficiency of LEDs with an enhancement of 78% but also collimate the view angle of LEDs from 131.5° to 114.0°. This could be because of the highly scattering nature of NVPCs which reduce the interference giving rise to Fabry-Perot resonance. Moreover, due to the threading dislocation suppression and strain relief by the NVPCs, the internal quantum efficiency was increased by 25% and droop behavior was reduced from 37.4% to 25.9%. The enhancement of light output power can be achieved as high as 151% at a driving current of 350 mA. Giant light output enhancement and directional control via NVPCs point the way towards a promising avenue of solid-state lighting.

Original languageEnglish
Pages (from-to)1192-1199
Number of pages8
JournalNanoscale
Volume8
Issue number2
DOIs
StatePublished - 14 Jan 2016

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    Tsai, Y. L., Liu, C. Y., Krishnan, C., Lin, D. W., Chu, Y. C., Chen, T. P., Shen, T. L., Kao, T-S., Charlton, M. D. B., Yu, P-C., Lin, C-C., Kuo, H-C., & He, J. H. (2016). Bridging the "green gap" of LEDs: Giant light output enhancement and directional control of LEDs via embedded nano-void photonic crystals. Nanoscale, 8(2), 1192-1199. https://doi.org/10.1039/c5nr05555e