Effects of nano-structured photonic crystals on light extraction enhancement of nitride light-emitting diodes

Wu, G.M.; Yen, Chih-Ta; Chien, H.W.; Lu, Hongxi; Chang, Tsung-Yao; Nee, Tzer‐En

doi:10.1016/j.tsf.2011.01.131

Cited by 12 publications

(9 citation statements)

References 11 publications

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“…Indeed, transmission losses due to total internal reflection are responsible for low light extraction efficiencies. Many surface structurations have been considered to overcome this specific problem [3][4][5][6][7][8][9][10][11][12]. For instance, roughness usually leads to diffraction, which provides new optical channels for light extraction.…”

Section: Introductionmentioning

confidence: 99%

Optimal overlayer inspired by Photuris firefly improves light-extraction efficiency of existing light-emitting diodes

Bay¹,

André²,

Sarrazin³

et al. 2013

Opt. Express

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In this paper the design, fabrication and characterization of a bioinspired overlayer deposited on a GaN LED is described. The purpose of this overlayer is to improve light extraction into air from the diode's high refractive-index active material. The layer design is inspired by the microstructure found in the firefly Photuris sp. The actual dimensions and material composition have been optimized to take into account the high refractive index of the GaN diode stack. This two-dimensional pattern contrasts other designs by its unusual profile, its larger dimensions and the fact that it can be tailored to an existing diode design rather than requiring a complete redesign of the diode geometry. The gain of light extraction reaches values up to 55% with respect to the reference unprocessed LED.

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Section: Introductionmentioning

confidence: 99%

Optimal overlayer inspired by Photuris firefly improves light-extraction efficiency of existing light-emitting diodes

Bay¹,

André²,

Sarrazin³

et al. 2013

Opt. Express

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“…Initial training of the genetic algorithm was done on simple 5,5] with a step ∆x i =0.01. The number n of parameters considered ranged between 2 and 6 as in this article.…”

Section: Discussionmentioning

confidence: 99%

“…[1,2,3] Many efforts actually focus on finding an efficient structuration of the surface in order to enhance the extraction of light. [4,5,6,7,8,9,10] Diffusion by surface roughness for example will open new optical channels for the extraction of light. [11] Some structurations specifically aim at achieving a graded refractive index at the surface in order to reduce total internal reflections.…”

Section: Introductionmentioning

confidence: 99%

Optimization by a genetic algorithm of the light-extraction efficiency of a GaN light-emitting diode

Mayer

Bay

2015

J. Opt.

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Light extraction from light-emitting materials is fundamentally limited by internal reflections due to the high dielectric-constant contrast between the material that produces the light and the emergent medium. These internal reflections can however be reduced significantly by a well-designed texturation of the surface of the emitting material. We used a genetic algorithm to determine optimal geometrical and material parameters for this texturation, the objective being to maximize the extraction of light of a GaN light-emitting diode (LED). This study, which was restricted to two-dimensional texturations, shows that symmetric triangles actually correspond to the optimal shape. The dielectric constant of the material used for this texturation should ideally have the same dielectric constant as the GaN. The optimal texturation determined in this work leads to a light-extraction efficiency of 11.1%, which improves significantly the value of 3.7% obtained with a flat surface and the value of 5.7% achieved in previous work.

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“…Therefore, to substantially enhance the LEE of the LED, various textured structures have been proposed to avoid the occurrence of total internal reflection, including rough surfaces, patterned substrates, diffraction gratings, and photonic crystals. Experiments have proven that these textured structures can enhance the LEE, and that they all appear to function in the same manner, namely by using light scattering effects to increase the probability of photon escape [3][4][5][6][7][8][9]. However, because research is typically conducted using trial and error during the manufacturing process, it is not easy to obtain the optimal structural parameters, nor is it possible to further understand the impact of the light scattering factor on the LEE.…”

Section: Introductionmentioning

confidence: 99%

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

Lee

Chou

2017

Energies

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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.

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Effects of nano-structured photonic crystals on light extraction enhancement of nitride light-emitting diodes

Cited by 12 publications

References 11 publications

Optimal overlayer inspired by Photuris firefly improves light-extraction efficiency of existing light-emitting diodes

Optimal overlayer inspired by Photuris firefly improves light-extraction efficiency of existing light-emitting diodes

Optimization by a genetic algorithm of the light-extraction efficiency of a GaN light-emitting diode

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

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