Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Self-Cleaning, Low-Reflectivity Surface Could Improve PV Cells

Image shows silicon pyramid structures etched for one minute using a hydrogen fluoride/hydrogen peroxide/water solution. The resulting structure has roughness at the micron and nanometer scales.
Image shows silicon pyramid structures etched for one minute using a hydrogen fluoride/hydrogen peroxide/water solution. The resulting structure has roughness at the micron and nanometer scales.

Abstract:
Micron- and Nanometer-Scale Features Make Superhydrophobic Surface

Self-Cleaning, Low-Reflectivity Surface Could Improve PV Cells

Atlanta, GA | Posted on April 8th, 2009

Using two different types of chemical etching to create features at both the micron and nanometer size scales, researchers at the Georgia Institute of Technology have developed a surface treatment that could boost the light absorption of silicon photovoltaic cells in two complementary ways.

The surface treatment increases absorption both by trapping light in three-dimensional structures and by making the surfaces self-cleaning - allowing rain or dew to wash away the dust and dirt that can accumulate on photovoltaic arrays. Because of its ability to make water bead up and roll off, the surface is classified as superhydrophobic.

"The more sunlight that goes into the photovoltaic cells and the less that reflects back, the higher the efficiency can be," said C.P. Wong, Regents' professor in Georgia Tech's School of Materials Science and Engineering. "Our simulations show that we can potentially increase the final efficiency of the cells by as much as two percent with this surface structure."

Supported by the National Science Foundation (NSF) and the National Electric Energy Testing Research and Applications Center (NEETRAC) at Georgia Tech, the research was described March 24th at the Spring 2009 National Meeting of the American Chemical Society in Salt Lake City.

The silicon etching treatment mimics the superhydrophobic surface of the lotus leaf, which uses surface roughness at two different size scales to create high contact angles that encourage water from rain or condensation to bead up and run off. As the water runs off, it carries with it any surface dust or dirt - which also doesn't adhere because of the unique surface properties.

In the silicon surface treatment, the two-tier roughness - created with both micron- and nano-scale structures - works in the same way as the lotus leaf, minimizing contact between the water or dust and the surface, Wong noted.

"When a water droplet reaches the surface, it sits on top of this two-tier roughness and only about three percent of it is in contact with the silicon," he explained.

Preparation of the superhydrophobic surface begins with use of a potassium hydroxide (KOH) solution to etch the silicon surface. The solution preferentially removes silicon along crystalline planes, creating micron-scale pyramid structures in the surface.

An e-beam process is then used to apply nanometer-scale gold particles to the pyramid structures. Using a solution of hydrogen fluoride (HF) and hydrogen peroxide (H2O2), a metal-assisted etching process - with gold as the catalyst - produces the nanometer-scale features. The feature size is controlled by the diameter of the gold particles and the length of time the silicon is exposed to the etching.

Finally, the gold is removed with a potassium iodide (KI) solution and the surface coated with a fluorocarbon material, perfluorooctyl tricholosilane (PFOS).

The combination of increased light absorption from the textured surface and the self-cleaning ability both help boost absorption of sunlight hitting the silicon surface.

"A normal silicon surface reflects a lot of the light that comes in, but by doing this texturing, the reflection is reduced to less than five percent," said Dennis Hess, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering. "As much as 10 percent of the light that hits the cells is scattered because of dust and dirt of the surface. If you can keep the cells clean, in principle you can increase the efficiency. Even if you only improve this by a few percent, that could make a big difference."

Even in desert areas where constant sunlight provides ideal conditions for photovoltaic arrays, nighttime dew should provide enough moisture to keep the cells clean, Wong said.

The research team, which also included Yonghao Xiu, Shu Zhang and Yan Liu, is working with Georgia Tech's University Center of Excellence for Photovoltaics Research and Education - headed by Professor Ajeet Rohatgi of the Georgia Tech School of Electrical and Computer Engineering - to evaluate the surface treatment with real solar cells.

However, adoption of the superhydrophobic surface treatment will ultimately depend on its long-term robustness and cost.

"Because the structures are so small, they are fairly fragile," Hess noted. "Mechanical abrasion to the surface can destroy the superhydrophobicity. We have tried to address that here by creating a large superhydrophobic surface area so that small amounts of damage won't affect the overall surface."

Large scale cost estimates haven't yet been done, but Hess said the additional etching and vacuum deposition steps shouldn't add dramatically to the already complex manufacturing process used for fabricating silicon PV cells.

In addition to photovoltaic cells, the surface treatment could be used to create anti-bacterial coatings on medical equipment, micro-electromechanical devices that don't stick together, and improved microfluidic devices.

Writer: John Toon


####

About Georgia Institute of Technology
The Georgia Institute of Technology is one of the nation's premier research universities. Ranked seventh among U.S. News & World Report's top public universities, Georgia Tech's more than 19,000 students are enrolled in its Colleges of Architecture, Computing, Engineering, Liberal Arts, Management and Sciences. Tech is among the nation's top producers of women and African-American engineers. The Institute offers research opportunities to both undergraduate and graduate students and is home to more than 100 interdisciplinary units plus the Georgia Tech Research Institute.

For more information, please click here

Contacts:
Research News & Publications Office
Georgia Institute of Technology
75 Fifth Street, N.W., Suite 100
Atlanta, Georgia 30308 USA

Media Relations Contacts:
John Toon
404-894-6986


or

Abby Vogel
404-385-3364


Technical Contacts: C.P. Wong (404-894-8391); E-mail: or Dennis Hess (404-894-5922); E-mail:

Copyright © Georgia Institute of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

GLOBALFOUNDRIES Announces Availability of 45nm RF SOI to Advance 5G Mobile Communications: Optimized RF features deliver high-performance solutions for mmWave beam forming applications in 5G smartphones and base stations February 22nd, 2017

EmTech Asia breaks new barriers with potential applications of space exploration with NASA and MIT February 22nd, 2017

JPK selects compact tensile stage from Deben for their NanoWizard® AFM platform to broaden capabilities for materials characterisation February 22nd, 2017

Molecular phenomenon discovered by advanced NMR facility: Cutting edge technology has shown a molecule self-assembling into different forms when passing between solution state to solid state, and back again - a curious phenomenon in science - says research by the University of Wa February 22nd, 2017

Strem Chemicals and Dotz Nano Ltd. Sign Distribution Agreement for Graphene Quantum Dots Collaboration February 21st, 2017

Chemistry

Molecular phenomenon discovered by advanced NMR facility: Cutting edge technology has shown a molecule self-assembling into different forms when passing between solution state to solid state, and back again - a curious phenomenon in science - says research by the University of Wa February 22nd, 2017

In-cell molecular sieve from protein crystal February 14th, 2017

Nano-level lubricant tuning improves material for electronic devices and surface coatings February 11th, 2017

Possible Futures

EmTech Asia breaks new barriers with potential applications of space exploration with NASA and MIT February 22nd, 2017

Tiny nanoclusters could solve big problems for lithium-ion batteries February 21st, 2017

Nominations Invited for $250,000 Kabiller Prize in Nanoscience: Major international prize recognizes a visionary nanotechnology researcher February 20th, 2017

Breakthrough with a chain of gold atoms: In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport February 20th, 2017

Nanomedicine

Nominations Invited for $250,000 Kabiller Prize in Nanoscience: Major international prize recognizes a visionary nanotechnology researcher February 20th, 2017

Good vibrations help reveal molecular details: Rice University scientists combine disciplines to pinpoint small structures in unlabeled molecules February 15th, 2017

In-cell molecular sieve from protein crystal February 14th, 2017

Cedars-Sinai, UCLA Scientists Use New ‘Blood Biopsies’ With Experimental Device to Speed Cancer Diagnosis and Predict Disease Spread: Leading-Edge Research Is Part of National Cancer Moonshot Initiative February 13th, 2017

Nanoelectronics

GLOBALFOUNDRIES Announces Availability of 45nm RF SOI to Advance 5G Mobile Communications: Optimized RF features deliver high-performance solutions for mmWave beam forming applications in 5G smartphones and base stations February 22nd, 2017

Particles from outer space are wreaking low-grade havoc on personal electronics February 19th, 2017

Liquid metal nano printing set to revolutionize electronics: Creating integrated circuits just atoms thick February 18th, 2017

1,000 times more efficient nano-LED opens door to faster microchips February 5th, 2017

Announcements

GLOBALFOUNDRIES Announces Availability of 45nm RF SOI to Advance 5G Mobile Communications: Optimized RF features deliver high-performance solutions for mmWave beam forming applications in 5G smartphones and base stations February 22nd, 2017

EmTech Asia breaks new barriers with potential applications of space exploration with NASA and MIT February 22nd, 2017

JPK selects compact tensile stage from Deben for their NanoWizard® AFM platform to broaden capabilities for materials characterisation February 22nd, 2017

Molecular phenomenon discovered by advanced NMR facility: Cutting edge technology has shown a molecule self-assembling into different forms when passing between solution state to solid state, and back again - a curious phenomenon in science - says research by the University of Wa February 22nd, 2017

Solar/Photovoltaic

Strem Chemicals and Dotz Nano Ltd. Sign Distribution Agreement for Graphene Quantum Dots Collaboration February 21st, 2017

'Lossless' metamaterial could boost efficiency of lasers and other light-based devices February 20th, 2017

Material can turn sunlight, heat and movement into electricity -- all at once: Extracting energy from multiple sources could help power wearable technology February 9th, 2017

NREL research pinpoints promise of polycrystalline perovskites February 8th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project