Structural Design for Enhanced Light Extraction in Light Emitting Diodes with Nano-patterned n-GaN

Park, Si-Hyun; Hong, Jun-Hee; Cui, Hao

doi:10.3938/jkps.57.812

Cited by 4 publications

(3 citation statements)

References 1 publication

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“…The light trapped by total internal reflection because of a large refractive index difference between the encapsulant and phosphor is a fundamental limiting factor of light extraction efficiency in LED packages . The critical angle of total internal reflection can be written using Snell's law as

{normalθ}_{normalcrit} = arcsin 1.623em1.623emtrue(\frac{n_{2}}{n_{1}} 1.623em1.623emtrue)

where n 1 and n 2 are the refractive indices of the phosphor and encapsulant, respectively. With the critical angle, it is possible to consider the region in the LED package through which light escapes into the air, and this region is called the light escape cone.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Glass Refractive Index on Light Extraction Efficiency of Light‐Emitting Diodes

Seo

Kim

et al. 2014

J. Am. Ceram. Soc.

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Light‐emitting‐diode (LED) encapsulants, such as epoxy and silicone resin, have a lower refractive index than YAG:Ce phosphor, and this is usually one of the major causes of LED inefficiency. To improve LED performance, a glass encapsulant is considered. In this study, the SiO2–B2O3–ZnO glass system containing La2O3 and WO3 was investigated as an encapsulant to minimize total internal reflection and to increase the light extraction efficiency of LED packages. The characterization of glass encapsulants was performed using a differential scanning calorimeter, a pycnometer, a prism coupler, X‐ray photoelectron spectroscopy, and integrating spheres. The refractive index increased linearly with increasing molar volume of glass because La2O3 and WO3 act as modifiers in the glass, creating more nonbridging oxygen. The refractive index of glass increases with the content of La2O3 and WO3, which is attributed to the increase in polarizability of oxide ions in the glass. When the refractive index between glass and phosphor matched, light extraction efficiency was maximized because total internal reflection decreased.

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{normalθ}_{normalcrit} = arcsin 1.623em1.623emtrue(\frac{n_{2}}{n_{1}} 1.623em1.623emtrue)

Section: Resultsmentioning

confidence: 99%

“…The light trapped by total internal reflection because of a large refractive index difference between the encapsulant and phosphor is a fundamental limiting factor of light extraction efficiency in LED packages. 5,10 The critical angle of total internal reflection can be written using Snell's law as 25,26 h crit ¼ arcsin…”

Section: Resultsmentioning

confidence: 99%

Effect of Glass Refractive Index on Light Extraction Efficiency of Light‐Emitting Diodes

Seo

Kim

et al. 2014

J. Am. Ceram. Soc.

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“…To obtain accurate simulation results, the spatial grid size must be small enough to resolve the smallest feature of the field, as well as represent the objects to be simulated [24]. In this Letter, we impose the condition Δ x ≤ ( λ o / n )/15, where Δ x , λ o and n are the spatial grid size, central wavelength of light and refractive index of the semiconductor material, respectively [25]. We use Δ t ≤ (Δ x / c )/2 for the temporal grid size, where c is the velocity of light.…”

Section: Numerical Simulation Proceduresmentioning

confidence: 99%

Numerical simulations of light‐extraction efficiencies of light‐emitting diodes on micro and nanopatterned sapphire substrates

Cui

Park

2014

Micro & Nano Letters

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Numerical simulations are performed to investigate the light-extraction efficiencies (LEEs) of gallium nitride-based light-emitting diodes (LEDs) on patterned sapphire substrates (PSSs), using the three-dimensional finite-difference time-domain method. PSSs with hexagonal arrays of cone-shaped patterns were used, and the pitch of the pattern array, pattern fill factor and pattern height were varied from nanoscale to microscale. The relative LEE for each PSS-LED was calculated, and the geometrical parameters were analysed for optimised light extraction enhancement of the PSS-LEDs.

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Study of light extraction efficiency of flip-chip GaN-based LEDs with different periodic arrays

Chen

Kong

et al. 2014

Optics Communications

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Structural Design for Enhanced Light Extraction in Light Emitting Diodes with Nano-patterned n-GaN

Cited by 4 publications

References 1 publication

Effect of Glass Refractive Index on Light Extraction Efficiency of Light‐Emitting Diodes

Effect of Glass Refractive Index on Light Extraction Efficiency of Light‐Emitting Diodes

Numerical simulations of light‐extraction efficiencies of light‐emitting diodes on micro and nanopatterned sapphire substrates

Study of light extraction efficiency of flip-chip GaN-based LEDs with different periodic arrays

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