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Energies 2017, 10(4), 424; doi:10.3390/en10040424

Scale-Dependent Light Scattering Analysis of Textured Structures on LED Light Extraction Enhancement Using Hybrid Full-Wave Finite-Difference Time-Domain and Ray-Tracing Methods

Graduate Institute of Color and Illumination Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan
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Author to whom correspondence should be addressed.
Academic Editor: Jean-Michel Nunzi
Received: 7 February 2017 / Revised: 14 March 2017 / Accepted: 20 March 2017 / Published: 23 March 2017
(This article belongs to the Special Issue Solid State Lighting)
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Abstract

A multiscale model that enables quantitative understanding and prediction of the size effect on the scattering properties of micro- and nanostructures is crucial for the design of light-emitting diode (LED) surface textures optimized for high light extraction efficiency (LEE). In this paper, a hybrid process for combining full-wave finite-difference time-domain simulation and a ray-tracing technique based on a bidirectional scattering distribution function model is proposed. We apply this method to study the influence of different pattern sizes of a patterned sapphire substrate on GaN-based LED light extraction from the micro-scale to the nano-scale. The results show that near-wavelength–scale patterns with strong diffraction are not expected to enhance the LEE. By contrast, micro-scale patterns with optical diffusion behavior have the highest LEE at a specific aspect ratio, and subwavelength-scale patterns that have antireflection properties show a marked enhancement of the LEE for a wide range of aspect ratios. View Full-Text
Keywords: light-emitting diodes; light extraction efficiency; textured structures; light scattering; bidirectional scattering distribution function (BSDF); bidirectional reflectance distribution function (BRDF); bidirectional transmittance distribution function (BTDF) light-emitting diodes; light extraction efficiency; textured structures; light scattering; bidirectional scattering distribution function (BSDF); bidirectional reflectance distribution function (BRDF); bidirectional transmittance distribution function (BTDF)
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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. (CC BY 4.0).

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Lee, T.-X.; Chou, C.-C. Scale-Dependent Light Scattering Analysis of Textured Structures on LED Light Extraction Enhancement Using Hybrid Full-Wave Finite-Difference Time-Domain and Ray-Tracing Methods. Energies 2017, 10, 424.

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