Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Stanford scientists see the solar future, and it's all about 'nanodomes' and 'plasmonics'

Acting like a waffle iron, silicon nanodomes, each about 300 nanometers in diameter and 200 nanometers tall, imprint a honeycomb pattern of nanoscale dimples into a layer of metal within the solar cell. Courtesy of Michael McGehee
Acting like a waffle iron, silicon nanodomes, each about 300 nanometers in diameter and 200 nanometers tall, imprint a honeycomb pattern of nanoscale dimples into a layer of metal within the solar cell. Courtesy of Michael McGehee

Abstract:
Stanford engineers dance with plasmonics to yield new direction for thin, inexpensive solar cells.

BY ANDREW MYERS

Stanford scientists see the solar future, and it's all about 'nanodomes' and 'plasmonics'

Stanford, CA | Posted on February 3rd, 2011

Researchers in solar energy speak of a day when millions of otherwise fallow square meters of sun-drenched roofs, windows, deserts and even clothing will be integrated with inexpensive solar cells that are many times thinner and lighter than the bulky rooftop panels familiar today.

So, when your iPod is on the nod, you might plug it into your shirt to recharge. Lost in the Serengeti with a sapped cell phone? No problem; rolled in your backpack is a lightweight solar pad. Sailing the seven seas and your GPS needs some juice? Hoist a solar sail and be one with the gods of geosynchronous orbit.

It is not hard to envision a time when such technologies will be ubiquitous in our increasingly energy-hungry lives. That day may come a bit sooner thanks to a multidisciplinary team of Stanford engineers led by Mike McGehee, Yi Cui and Mark Brongersma, and joined by Michael Graetzel at the École Polytechnique Fédérale de Lausanne (EPFL).

Waves of energy

In an article published in Advance Energy Materials, the Stanford/EPFL team announced a new type of thin solar cell that could offer a new direction for the field. They succeeded in harnessing plasmonics - an emerging branch of science and technology - to more effectively trap light within thin solar cells to improve performance and push them one step closer to daily reality.

"Plasmonics makes it much easier to improve the efficiency of solar cells," said McGehee, an associate professor of materials science and engineering at Stanford.

McGehee is the director of CAMP - the Center for Advanced Molecular Photovoltaics - a multidisciplinary, multi-university team tackling the challenges of thin-film solar cells.

"Using plasmonics we can absorb the light in thinner films than ever before," McGehee said. "The thinner the film, the closer the charged particles are to the electrodes. In essence, more electrons can make it to the electrode to become electricity."

Plasmonics is the study of the interaction of light and metal. Under precise circumstances, these interactions create a flow of high-frequency, dense electrical waves rather than electron particles. The electronic pulse travels in extremely fast waves of greater and lesser density, like sound through the air.

A perfect solar waffle

The lightbulb moment for the team came when they imprinted a honeycomb pattern of nanoscale dimples into a layer of metal within the solar cell. Think of it as a nanoscale waffle, only the bumps on the waffle iron are domes rather than cubes - nanodomes to be exact, each only a few billionths of a meter across.

To fashion their waffle, McGehee and team members spread a thin layer of batter on a transparent, electrically conductive base. This batter is mostly titania, a semi-porous metal that is also transparent to light. Next, they use their nano waffle iron to imprint the dimples into the batter. Next, they layer on some butter - a light-sensitive dye - which oozes into the dimples and pores of the waffle. Lastly, the engineers add some syrup - a layer of silver, which hardens almost immediately.

When all those nanodimples fill up, the result is a pattern of nanodomes on the light-ward side of the silver.

This bumpy layer of silver has two primary benefits. First, it acts as a mirror, scattering unabsorbed light back into the dye for another shot at collection. Second, the light interacts with the silver nanodomes to produce plasmonic effects. Those domes of silver are crucial. Reflectors without them will not produce the desired effect. And any old nanodomes won't do either; they must be just the right diameter and height, and spaced just so, to fully optimize the plasmonics.

If you imagine your nanoself observing one of these solar cells in slow motion, you would see photons enter and pass through the transparent base and the titania (the waffle), at which point some photons would be absorbed by the light-sensitive dye (the butter), creating an electric current. Most of the remaining photons would hit the silver back reflector (the hardened syrup) and bounce back into the solar cell. A certain portion of the photons that reach the silver, however, will strike the nanodomes and cause plasmonic waves to course outward. And there you have it - the first-ever plasmonic dye-sensitized solar cell.

Trapping the light fantastic

It is easy to see why researchers are focused on thin-film solar technology. In recent years, much hope has been directed toward these lightweight, flexible cells that use photosensitive dyes to generate electricity. These cells have many advantages: They are less energy intensive and less costly to produce, flowing like newsprint off huge roll presses. They are thinner even than other "thin" solar cells. They are also printable on flexible bases that can be rolled up and taken virtually anywhere. Many use non-toxic, abundantly available materials, as well - a huge plus in the push for sustainability.

Dye-sensitized solar cells are not without challenges, however. First off, the very best convert only a small percentage of light into electricity - about 8 percent. The bulkier commercial technologies available today have reached 25 percent efficiency, and certain advanced applications have topped 40 percent. And then there is durability. The latest thin solar cell will last about seven years under continuous exposure to the elements. Not bad until you consider that 20 to 30 years is the commercial standard.

Both efficiency and reliability will have to improve. Nonetheless, engineers like McGehee believe that if they can convert just 15 percent of the light into electricity - a figure that is not out of reach - and tease the lifespan to a decade, we might soon find ourselves in the age of personal solar cells. An advance like plasmonics just might provide the spark necessary to take the field down a new and exciting path.

A matter of economics

Cheaper and cleaner will be the keys. Coal-based power is plentiful and cheap, but also comes at a steep environmental cost in gouged landscapes and polluted skies. At today's commercial rates, however, even the best solar alternatives cost five times more per kilowatt-hour than coal. It is clear that economics, and not technology, is what stands between us and our solar future.

But McGehee and others are confident they can make thin solar cells more attractive.

Andrew Myers is the associate communications director for the School of Engineering.

####

For more information, please click here

Contacts:
Media Contact
Andrew Myers
Stanford School of Engineering
(650) 736-2245

Copyright © Stanford University

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

Three-dimensional graphene: Experiment at BESSY II shows that optical properties are tuneable May 24th, 2017

Leti to Demo 1st Wireless UNB Transceiver for ‘Massive Internet of Things’ at RFIC 2017 and IMS 2017: Leti Will also Present Three Papers & Two Workshops on 5G Communications IC Design, from RF to mm-Wave, During IMS 2017 and RFIC 2017 in Hawaii May 24th, 2017

GLOBALFOUNDRIES and Chengdu Partner to Expand FD-SOI Ecosystem in China: More than $100M investment to establish a center of excellence for FDXTM FD-SOI design May 23rd, 2017

Zap! Graphene is bad news for bacteria: Rice, Ben-Gurion universities show laser-induced graphene kills bacteria, resists biofouling May 22nd, 2017

Thin films

Discovery of new transparent thin film material could improve electronics and solar cells: Conductivity is highest-ever for thin film oxide semiconductor material May 6th, 2017

MIT Energy Initiative awards 10 seed fund grants for early-stage energy research May 4th, 2017

Nanomechanics, Inc. Unveils New Product at ICMCTF Show April 25th: Nanoindentation experts will launch the new Gemini that measures the interaction of two objects that are sliding across each other – not merely making contact April 21st, 2017

Nanomechanics Inc. President Warren Oliver, PhD to Present at ICMCTF: Nanoindentation experts will discuss new testing system that measures the interaction of two objects that are sliding across each other – not merely making contact April 17th, 2017

Possible Futures

Three-dimensional graphene: Experiment at BESSY II shows that optical properties are tuneable May 24th, 2017

GLOBALFOUNDRIES and Chengdu Partner to Expand FD-SOI Ecosystem in China: More than $100M investment to establish a center of excellence for FDXTM FD-SOI design May 23rd, 2017

Zap! Graphene is bad news for bacteria: Rice, Ben-Gurion universities show laser-induced graphene kills bacteria, resists biofouling May 22nd, 2017

Leti Will Demo World’s-first WVGA 10-µm Pitch GaN Microdisplays for Augmented Reality Video at Display Week in Los Angles: Invited Paper also Will Present Leti’s Success with New Augmented Reality Technology That Reduces Pixel Pitch to Less than 5 Microns May 22nd, 2017

Academic/Education

MIT Energy Initiative awards 10 seed fund grants for early-stage energy research May 4th, 2017

Bar-Ilan University to set up quantum research center May 1st, 2017

California Research Alliance by BASF establishes more than 25 research projects in three years April 26th, 2017

SUNY Polytechnic Institute Announces Total of 172 Teams Selected to Compete in Solar in Your Community Challenge: Teams from 40 states, plus Washington, DC, 2 Territories, and 4 American Indian Reservations, Will Deploy Solar in Underserved Communities April 20th, 2017

Announcements

Three-dimensional graphene: Experiment at BESSY II shows that optical properties are tuneable May 24th, 2017

Leti to Demo 1st Wireless UNB Transceiver for ‘Massive Internet of Things’ at RFIC 2017 and IMS 2017: Leti Will also Present Three Papers & Two Workshops on 5G Communications IC Design, from RF to mm-Wave, During IMS 2017 and RFIC 2017 in Hawaii May 24th, 2017

GLOBALFOUNDRIES and Chengdu Partner to Expand FD-SOI Ecosystem in China: More than $100M investment to establish a center of excellence for FDXTM FD-SOI design May 23rd, 2017

Zap! Graphene is bad news for bacteria: Rice, Ben-Gurion universities show laser-induced graphene kills bacteria, resists biofouling May 22nd, 2017

Energy

Three-dimensional graphene: Experiment at BESSY II shows that optical properties are tuneable May 24th, 2017

Stanford scientists use nanotechnology to boost the performance of key industrial catalyst May 18th, 2017

Fed grant backs nanofiber development: Rice University joins Department of Energy 'Next Generation Machines' initiative May 10th, 2017

Discovery of new transparent thin film material could improve electronics and solar cells: Conductivity is highest-ever for thin film oxide semiconductor material May 6th, 2017

Solar/Photovoltaic

Three-dimensional graphene: Experiment at BESSY II shows that optical properties are tuneable May 24th, 2017

Stanford scientists use nanotechnology to boost the performance of key industrial catalyst May 18th, 2017

Fed grant backs nanofiber development: Rice University joins Department of Energy 'Next Generation Machines' initiative May 10th, 2017

Discovery of new transparent thin film material could improve electronics and solar cells: Conductivity is highest-ever for thin film oxide semiconductor material May 6th, 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