06 light management by nano materials-huis in t veld, kriya materials

Kriya Materials, general presentation 1


Light management by nano materials

Optical coatings for managing light propagation in “lighting”, “display” and other application areas

Kriya Materials, general presentation

Overview • General introduction Kriya Materials • Anti-Reflection coating

– Classical AR models • Single layer • Double layer • Multi layer

– AR coating developed by Kriya Materials • 1-pot AR (unique feature)

• Light coupling

– Light in-coupling for Solar – Light out-coupling for LED/OLED/Display

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General introduction Kriya Materials Started in 2006 at Chemelot Campus, The Netherlands Develops and manufactures custom made functional coatings based

upon its own nano particles for various markets, Active in various fields following a set of global trends;

Lighting; Led and oled; Improving energy efficiency Agro greenhouses; Chemical reduction, plant growth regulation Energy conservation; Building and cars, by climate control film

coatings Energy production solar; Functional coatings for solar panels,

improving efficiency levels Display materials; Functional coatings, wide range

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Anti-Reflection coating Method for Anti-Reflection (AR); “To lower the Fresnel reflection losses which are always present at any interface separating different indices of reflection”. • Classical AR models

– Single layer – Double layer – Multi layer

• AR coating developed by Kriya Materials – 1-pot AR (unique feature)

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Classical AR models Single layer • Optimal RI of the coating layer is midway between that of the surrounding

medium n0 and the substrate n2 e.g. MgF2 (n = 1.37[2])

• Optimal layer thickness is one-quarter wavelength[1]

– Based on a single layer of low RI (n) material and thickness (d) • Reduces reflection at a specific (targeted) wavelength (λ/4[1]) • Reflection at non-targeted wavelengths is never greater than the

reflection of the untreated substrate • Drawback of this technique

– No suitable material with low enough RI and sufficient mechanical hardness available

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AR coating; n1, λ/4 Substrate; n2

Medium (air); n0


Classical AR models Double layer • Based on two layers with contrasting refractive indexes

– Low RI layer e.g. MgF2 (n=1.37[2]) on high RI layer e.g. ZnS (n=2.37[3]) – Drawback of this technique

• Reflection at non-targeted wavelengths can be higher than the reflection of the uncoated substrate

– Optimal layer thickness is one quarter wavelength for each separate layer[1]

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High RI coating; n2, λ/4 Substrate; n3

Medium (air); n0 Low RI coating; n1, λ/4


Classical AR models Multi layer • Based on three or more layers of low, medium and high refractive indexes

– Stack for three layers is • n1 low RI coating • n2 high RI coating • n3 medium RI coating

– Optimal layer thickness is; one quarter wavelength for n1, one half wavelength for n2 and one quarter wavelength for n3[1]

• General rule of thumb, more layers = less reflection = higher production cost

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Medium RI coating; n3, λ/4 Substrate; n4

High RI coating; n2, λ/2

Medium (air); n0 Low RI coating; n1, λ/4


AR coating developed by Kriya Materials • 1-pot AR coating (unique feature)

– Innovative solution to apply a single wet coating layer – Production cost of a single layer AR with the effectiveness of a double

layer AR

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1-pot AR coating • Deposition of a single wet coating layer

– Contains various special modified nanoparticle materials • Nanoparticle materials are developed and produced at Kriya

Materials • Applicable on various plastic substrates

– PET, PC and TAC have been tested so far • Innovative solution to overcome high production cost

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1-pot AR coating

Reflection spectra of Kriya’s 1-pot AR coating on TAC and PC (both sides coated). Data recorded with a Ocean Optics USB2000 detector

Thickness ≈150 nm. Rmin = 4λ = 600 nm


Light coupling • Light in-coupling

– Promotion of light refraction towards an absorber

• Light out-coupling – Promotion of light extraction from a light source

• Similar approach for in- and out-coupling


Light in-coupling for Solar • Promoting the light in-coupling for solar cels through a refractive index

matched textured resist

• Increasing the efficiency of CIGS solar cels – Standard practice is to apply a textured resist (polymeric coating) e.g.

Moth eye structure[4]

– Additional efficiency gain by increasing the refractive index of the textured resist[5]

In collaboration with TNO[5]


Light in-coupling for Solar • Textured resist

– Textured resist is produced through Nano Imprint Lithography (NIL)

– Decreases the reflection at the interface which increases the amount of

photons – By matching the refractive index of the resist to that of the AZO layer,

reflection losses at the resist/AZO interface are minimalized

Schematic representation of a CIGS solar cell (a) without and (b) with textured resist[5]


Light in-coupling for Solar • Schematic representation of the reflection on a non-textured resist and

textured resist

Non-textured resist, x% reflected

Textured resist, x% reflected which is partially “re-used”.

Typical increase of absorption is about 25% through use of a textured structure

Light propagation

“Normal”


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Light in-coupling for Solar

Reflection of AZO on glass (blue), AZO on glass coated with non-textured resist (green) and AZO on glass coated with textured resist (red).[5]

Integral reflection 300-1100 nm AZO on glass (blue) R=14.5% AZO on glass non-textured resist (green) R=13.3% AZO on glass textured resist (red) R=5.7%


Light coupling ✔ Light in-coupling

– Promotion of light refraction towards an absorber

• Light out-coupling – Promotion of light extraction from a light source

• Mechanism similar approach for in- and out-coupling


Light out-coupling for LED/OLED/Displays • Promoting the light out-coupling in various applications by refractive index

matching

(a) Escape cone of a LED without and with encapsulation[6]

(b) Light-extraction efficiency ratio for GaN and GaP as a function of the encapsulant refractive index[6]

Kriy

a R

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References [1] Nave, R. (2014) Anti-Reflection Coatings. Retrieved from: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/antiref.html [2] Optical constants of MgF2 (Magnesium fluoride), Li 1980. Retrieved from: http://refractiveindex.info [3] Optical constants of ZnS (Zinc sulfide), Debenham 1984 - Cubic ZnS. Retrieved from: http://refractiveindex.info [4] Al-Turk, S. (2011) Analytic optimization modeling of Anti-Reflection coatings for Solar Cells. Master’s thesis. MC Master University,

United Status of America. [5] Burghoorn, M., Kniknie, B., van Deelen, J., Xu, M., Vroon, Z., van Ee, R., van de Belt, R., and Buskens, P. (2014) Improving the

efficiency of copper indium gallium (Di)selenide (CIGS) solar cells through integration of a moth-eye textured resist with a refractive index similar to aluminium doped zinc oxide. AIP ADVANCES. 4 (127154), 127154-1 – 127154-7.

[6] Mont, F.W. et al. (2008) High refractive index TiO2 nanoparticle-loaded encapsulants for LED. J. Appl. Phys, 103 (083120), 083120-1 - 083120-6.

http://refractiveindex.info/

06 light management by nano materials-huis in t veld, kriya materials

Technology

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