Optimizing textured structures possessing both optical gradient and diffraction properties to increase the extraction efficiency of light-emitting diodes

Hsu, Cheng-Wei; Lee, Yang–Chun; Chen, Hsuen‐Li; Chou, Y.C.

doi:10.1016/j.photonics.2012.04.005

Cited by 15 publications

(8 citation statements)

References 29 publications

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“…Such a result is really promising when considered against usual patterned devices found in the literature addressing LED light extraction, where two kinds of devices are usually considered. The first one comprises subwavelength structures, which act as an optical adaption layer with an effective optical index gradient [13][14][15]. The other presents micrometric patterns which do not exceed 1 or 2 microns.…”

Section: B Led Bioinspired Pattern and Optimizationmentioning

confidence: 99%

“…For instance, roughness usually leads to diffraction, which provides new optical channels for light extraction. Nanostructures are also considered, to mimic a layer with a graded refractive index [13][14][15], another way to reduce abrupt refractive index contrast and increase the light extraction efficiencies. Finally, another approach considers microstructures which act as tiny lenses or other optical devices to guide light out of the LED [16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…Fireflies produce their own light, which needs to be extracted from photocytes found in its bioluminescent organ (called "lantern"). It has been shown in previous works [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] that the firefly Photuris sp. presents a two-dimensional pattern with an asymmetrical triangular profile with sizes in the range of a few micrometers on its lantern cuticle.…”

Section: Introductionmentioning

confidence: 99%

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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: B Led Bioinspired Pattern and Optimizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Bay¹,

André²,

Sarrazin³

et al. 2013

Opt. Express

View full text Add to dashboard Cite

show abstract

“…Nonetheless, due to the nature of the microbial growth, these lenses are closed packed. In the literature related to light out-coupling from GaN:LEDs, close packed conical structures have been reported to be optimal antireflective structures because of the refractive index gradient formed at the air-substrate interface 20 . Similarly, among various aspherical micro-lenses prepared by multistep lithography, the best curve profile for extraction of light was a parabola 21 .…”

Section: Applications: Engineering Opportunitiesmentioning

confidence: 99%

Fabrication of three dimensional patterns of wide dimensional range using microbes and their applications

Mehta

Murugeson

Prakash

2015

Sci Rep

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Inspired by the wound healing property of certain trees, we report a novel microbes based additive process for producing three dimensional patterns, which has a potential of engineering applications in a variety of fields. Imposing a two dimensional pattern of microbes on a gel media and allowing them to grow in the third dimension is known from its use in biological studies. Instead, we have introduced an intermediate porous substrate between the gel media and the microbial growth, which enables three dimensional patterns in specific forms that can be lifted off and used in engineering applications. In order to demonstrate the applicability of this idea in a diverse set of areas, two applications are selected. In one, using this method of microbial growth, we have fabricated microlenses for enhanced light extraction in organic light emitting diodes, where densely packed microlenses of the diameters of hundreds of microns lead to luminance increase by a factor of 1.24X. In another entirely different type of application, braille text patterns are prepared on a normal office paper where the grown microbial colonies serve as braille tactile dots. Braille dot patterns thus prepared meet the standard specifications (size and spacing) for braille books.

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“…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 [12][13][14][15]. Surface plasmonics [16] is also used to facilitate the extraction of light.…”

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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Optimizing textured structures possessing both optical gradient and diffraction properties to increase the extraction efficiency of light-emitting diodes

Cited by 15 publications

References 29 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

Fabrication of three dimensional patterns of wide dimensional range using microbes and their applications

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

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