High-performance antireflection coatings utilizing nanoporous layers

Poxson, David J.; Kuo, Mei-Ling; Mont, Frank W.; Kim, Y.-S.; Yan, Xing; Welser, Roger E.; Sood, Ashok K.; Cho, Jaehee; Lin, Shawn‐Yu; Schubert, E. Fred

doi:10.1557/mrs.2011.110

Cited by 50 publications

(48 citation statements)

References 31 publications

(22 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Thus, unless they are encapsulated, this effect precludes their straightforward incorporation into real-world optical devices [48]. Surprisingly, this effect has been generally overlooked in many works regarding the use of OAD thin films as an antireflective coating or multilayer in solar cells or other related environmental applications [236][237][238]. On the other hand, the development of humidity sensors takes advantage of this very change in the optical constants of OAD films and multilayers due to the adsorption of water vapor from the atmosphere [78].…”

Section: Porosity and Adsorption Propertiesmentioning

confidence: 99%

“…Thus, in order to reduce the light reflection coefficient and increase the amount of transmitted light, antireflection coatings (AR) are usually incorporated on the front side of these devices. Because of their high porosity (see Section 3.6), OAD thin films and multilayer structures have an inherently low refraction index, making them suitable for AR-layer applications [331,332,335]. An added benefit of ITO OAD films used for this purpose resides in their high electrical conductivity.…”

Section: Solar Cell Componentsmentioning

confidence: 99%

“…Photon harvesting in photoactive solar cell components substantially increases if light is scattered or confined within the system, and so the implementation of an AR coating at the front side of a solar cell is a well-known method of confinement that enhances light absorption by the active material. Since sunlight has a broad spectrum and its angle of incidence changes throughout the day, highperformance AR coatings must be efficient over the entire solar spectrum and a wide range of incident angles [335]. A good approach to avoid Fresnel reflections (i.e.…”

Section: Ar Coatingsmentioning

confidence: 99%

“…In terms of their optical properties, this means that either by alternating the type of deposited material and/or changing the densification, the refractive index profile along the film thickness can be effectively tuned. This possibility has been used to fabricate antireflection coatings [236,496,497] and rugate filters that are characterized by a sinusoidal index profile [90,92,498,499]. One-dimensional photonic crystals (also designated as Bragg stacks) and Bragg microcavities have also been fabricated by successively stacking oxides of different refractive indices (e.g., low index SiO 2 and high index TiO 2 ) [285,[500][501][502] or with porous-graded Si posteriorly oxidized by high temperature annealing [503].…”

Section: Passive Optical Applicationsmentioning

confidence: 99%

See 3 more Smart Citations

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

Barranco

Borrás

González‐Elipe

et al. 2016

Progress in Materials Science

583

436

View full text Add to dashboard Cite

a b s t r a c tThe oblique angle configuration has emerged as an invaluable tool for the deposition of nanostructured thin films. This review develops an up to date description of its principles, including the atomistic mechanisms governing film growth and nanostructuration possibilities, as well as a comprehensive description of the applications benefiting from its incorporation in actual devices. In contrast with other reviews on the subject, the electron beam assisted evaporation technique is analyzed along with other methods operating at oblique angles, including, among others, magnetron sputtering and pulsed laser or ion beam-assisted deposition techniques. To account for the existing differences between deposition in vacuum or in the presence of a plasma, mechanistic simulations are critically revised, discussing well-established paradigms such as the tangent or cosine rules, and proposing new models that explain the growth of tilted porous nanostructures. In the second part, we present an extensive description of applications wherein oblique-angle-deposited thin films are of relevance. From there, we proceed by considering the requirements of a large number of functional devices in which these films are currently being utilized (e.g., solar cells, Li batteries, electrochromic glasses, biomaterials, sensors, etc.), and subsequently describe how and why these nanostructured materials meet with these needs.

show abstract

Section: Porosity and Adsorption Propertiesmentioning

confidence: 99%

Section: Solar Cell Componentsmentioning

confidence: 99%

Section: Ar Coatingsmentioning

confidence: 99%

Section: Passive Optical Applicationsmentioning

confidence: 99%

See 2 more Smart Citations

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

Barranco

Borrás

González‐Elipe

et al. 2016

Progress in Materials Science

583

436

View full text Add to dashboard Cite

show abstract

“…The use of porous nanostructured materials to minimize reflection losses has recently been studied by Prof. Fred Schubert's group at the Rensselaer Polytechnic Institute (RPI) [9]. Their work has explored the possibility of using nanowires grown by the oblique angle deposition technique to create advanced antireflection structures.…”

Section: Oblique Angle Depositionmentioning

confidence: 99%

Development of Nanostructured Antireflection Coatings for EO/IR Sensor and Solar Cell Applications

Sood¹,

Sood²,

Welser³

et al. 2012

MSA

Self Cite

View full text Add to dashboard Cite

Electro-optical/infrared (EO/IR) sensors and photovoltaic power sources are being developed for a variety of defense and commercial applications. One of the critical technologies that will enhance both EO/IR sensor and photovoltaic module performance is the development of high quality nanostructure-based antireflection coatings. In this paper, we review our work on advanced antireflection structures that have been designed by using a genetic algorithm and fabricated by using oblique angle deposition. The antireflection coatings are designed for the wavelength range of 250 nm to 2500 nm and an incidence angle between 0˚ and 40˚. These nanostructured antireflection coatings are shown to enhance the optical transmission through transparent windows over a wide band of interest and minimize broadband reflection losses to less than one percent, a substantial improvement over conventional thin-film antireflection coating technologies.

show abstract

Environmentally Tight TiO₂–SiO₂ Porous 1D‐Photonic Structures

García-Valenzuela

López‐Santos

Rico

et al. 2018

Adv Materials Inter

View full text Add to dashboard Cite

materials with different refractive indexes (e.g., TiO 2 and SiO 2 ), has been proposed as a way of tailoring the optical behavior of broadband antireflection coatings used to maximize the performance of photovoltaic cells. [8] Porosity is also a key characteristic when preparing Bragg stacks acting as optical and optofluidic sensors for the detection of vapors or for liquid monitoring, respectively. [9] According to the principles of the effective medium approximation theory, [10] porosity can be utilized to adjust the overall refraction index of thin films as an average of the contributions of air (n air = 1.0) and film material (i.e., n b ). However, the adjustment of the optical properties of porous films faces the critical problem of their environmental instability due to the condensation of water (n w = 1.31) and other vapors into their open pores. Although this effect has been utilized for the optical detection of vapors using stacks of thin films in the form of Bragg structures, [9a,b,10] the affectation of optical properties in multilayers acting as 1D photonic structures can be a serious problem when dealing with passive optical systems. [12] This is clear in solar cells and other outdoor applications where optical instabilities due to water condensation have to be suppressed by polymer encapsulation during device assembly. In the present work, we propose the use porosity as an additional parameter to control the optical properties of multilayer stacks but, simultaneously, ensuring its environmental tightness and therefore, a stable outdoor functioning. To enhance film porosity we use the technique of magnetron sputtering at oblique angles (MS-OAD). [13] This geometrical configuration, either by e-beam evaporation or magnetron sputtering (MS), induces the growth of nanocolumnar films with porosities that may reach up to 50-60% of the film volume. [14] Highly porous OAD films and multilayers have been utilized in the pass for the fabrication of antireflection layers for passive optical applications, [7,11a,b] photo catalytic layers, [5,10a] humidity and other vapor sensors [10a,b,15] or optofluidic devices. [9c,d,16] Herein, we firstly prove that the optical behavior of MS-OAD multilayers in the form of Bragg reflectors (BR) or Bragg microcavities (BM) can be tailored by adjusting the porosity of the TiO 2 and SiO 2 thin films (e.g., making the TiO 2 compact and the SiO 2 highly porous, as proposed in previous works [7,12c] ). Then, using an optical monitoring procedure previously applied to study vapor Although thin film porosity is the basis of many optical sensors, it can be deleterious for a stable optical behavior of passive optical elements due to the condensation of water and other vapors in their pores. This paper proposes a new strategy for the magnetron sputtering (MS) fabrication of environmentally tight SiO 2 -TiO 2 porous multilayers. Thin films of these two oxides deposited in an oblique angle configuration (MS-OAD) present a nanocolumnar and highly porous nanostructure and, as ...

show abstract

High-performance antireflection coatings utilizing nanoporous layers

Abstract: Abstract

Cited by 50 publications

References 31 publications

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

Development of Nanostructured Antireflection Coatings for EO/IR Sensor and Solar Cell Applications

Environmentally Tight TiO₂–SiO₂ Porous 1D‐Photonic Structures

Contact Info

Product

Resources

About

High-performance antireflection coatings utilizing nanoporous layers

Abstract: Abstract

Cited by 50 publications

References 31 publications

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

Development of Nanostructured Antireflection Coatings for EO/IR Sensor and Solar Cell Applications

Environmentally Tight TiO2–SiO2 Porous 1D‐Photonic Structures

Contact Info

Product

Resources

About

Environmentally Tight TiO₂–SiO₂ Porous 1D‐Photonic Structures