Bridging “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 Charlton, Peichen Yu, Chien-Chung Lin, Hao-Chung Kuo, Jr-Hau He

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


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 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 boosting light extraction efficiency of LEDs with an enhancement of 78% but also collimating the view angle of LEDs from 131.5゜to 114.0゜. This could be because 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 points the way towards a promising avenue of solid-state lighting.
Original languageEnglish (US)
Pages (from-to)1192-1199
Number of pages8
Issue number2
StatePublished - 2016

Cite this