Nanotechnology Now





Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Like a hall of mirrors, nanostructures trap photons inside ultrathin solar cells

Abstract:
In the quest to make sun power more competitive, researchers are designing ultrathin solar cells that cut material costs. At the same time they're keeping these thin cells efficient by sculpting their surfaces with photovoltaic nanostructures that behave like a molecular hall of mirrors.

Like a hall of mirrors, nanostructures trap photons inside ultrathin solar cells

Stanford, CA | Posted on April 22nd, 2014

"We want to make sure light spends more quality time inside a solar cell," said Mark Brongersma, a professor of materials science and engineering at Stanford and co-author of a review article in Nature Materials.

Brongersma and two Stanford colleagues -- associate professor of materials science and engineering Yi Cui and professor of electrical engineering Shanhui Fan -- surveyed 109 recent scientific papers from teams around the world.

Their overview revolves around a basic theme: looking at the many different ways that researchers are trying to maximize the collisions between photons and electrons in the thinnest possible layers of photovoltaic materials. The goal is to reveal trends and best practices that will help drive developments in the field.

Solar energy is produced when photons of light collide with the electrons in a photovoltaic crystal. As loose electrons move through the crystal, they generate an electrical current.

Today's solar cells are already thin. They are made up of layers of photovoltaic materials, generally silicon, that average 150 to 300 micrometers, which is roughly the diameter of two to three human hairs.

As engineers continue to shave down those dimensions they have to develop new molecular traps and snares to ensure that photons don't simply whiz through their ultrathin solar cells before the electrical sparks can fly.

"A lot of the excitement now is about using the principles of photonics to manage light waves in the most efficient way," Fan said. "There are perhaps hundreds of groups in the world working on this."

The review article provides a high level view of how scientists are trying to design structures to facilitate interactions between the infinitesimal instigators of solar current, the photons and the electrons.

Research face enormous challenges in trying to architect nanostructures attuned to catch light. Sunlight consists of many colors. When we see rainbow, what we see is result of atmospheric moisture acting as a prism to bend light into its constituent colors. Creating different nanostructures to catch the pot of photons at the end of each color of the rainbow is part of what this research is about.

Nevertheless, scientists are already reporting some success

"We are seeing systems that use one one-hundredth as much photovoltaic material as today's solar cells while getting 60 percent to 70 percent of the electrical output," Brongersma said.

The most common photovoltaic material is a refined form of silicon similar to that found in computer chips. This material accounts for 10 percent to 20 percent of a solar cell's cost. Lowering those expenses 100-fold would therefore have a considerable effect on the overall cost-efficiency of solar energy production.

But Cui says lowering material costs is only part of the push behind ultrathin solar. Another benefit is flexibility. Because of the thickness of the light-catching silicon layer, today's solar cells must be kept rigid lest their crystal lattice be damaged and the flow of electrons disrupted.

"But at 10 micrometers of thickness silicon has a high degree of mechanical flexibility," said Cui, citing a dimension less than one-tenth the thickness of the photovoltaic layer inside today's solar cells.

Cui, who has made just such an experimental material, shows a movie of flapping this thin silicon like a piece of paper and cutting it with a scissors (see separate videos; flapping www.youtube.com/watch?v=e71Z0Kt3bsQ and cutting www.youtube.com/watch?v=PFyKfkwPRfs). Those thin silicon strips incorporate some of the photon-trapping nanostructures described in the Nature Materials article. Cui says the light-to-energy conversion efficiency of thin silicon is approaching that of the rigid silicon in today's solar cells.

Flapping silicon isn't just a science project. Such flexibility would pay a dividend when it comes to installation, which accounts for roughly one-third of the total cost of a rooftop solar array. "These thin silicon cells can be embedded into flexible plastic, making installation like rolling out a carpet," Cui said.

Yet even as researchers succeed in getting more from less, many hurdles remain according to Fan, who develops computer models to study how different nanostructures and materials will affect photon-electron interactions.

"There are an infinite number of structures, so it isn't possible to model them all," he said, alluding to what he called the "theoretical bottlenecks" that impede scientific understanding of this ethereal realm where light and matter intersect.

"For instance, right now, we really don't have a way to know when we've gotten the most out of our photons," Fan said.

###

Tom Abate is Associate Director of Communications at Stanford Engineering

####

For more information, please click here

Contacts:
Tom Abate

650-736-2245

Copyright © Stanford School of Engineering

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

A 'movie' of ultrafast rotating molecules at a hundred billion per second: A quantum wave-like nature was successfully observed in rotating nitrogen molecules July 4th, 2015

New Biosensor Produced in Iran to Detect Effective Drugs in Cancer Treatment July 4th, 2015

Clues to inner atomic life from subtle light-emission shifts: Hyperfine structure of light absorption by short-lived cadmium atom isotopes reveals characteristics of the nucleus that matter for high precision detection methods July 3rd, 2015

Pioneering Southampton scientist awarded prestigious physics medal July 3rd, 2015

Videos/Movies

A 'movie' of ultrafast rotating molecules at a hundred billion per second: A quantum wave-like nature was successfully observed in rotating nitrogen molecules July 4th, 2015

Freezing single atoms to absolute zero with microwaves brings quantum technology closer: Atoms frozen to absolute zero using microwaves July 2nd, 2015

NIST Group Maps Distribution of Carbon Nanotubes in Composite Materials July 2nd, 2015

Compact, Low Cost, Accurate: Mini Positioning Stages, by PI June 30th, 2015

Thin films

New micro-supercapacitor structure inspired by the intricate design of leaves: A team of scientists in Korea has devised a new method for making a graphene film for supercapacitors July 2nd, 2015

Discoveries

A 'movie' of ultrafast rotating molecules at a hundred billion per second: A quantum wave-like nature was successfully observed in rotating nitrogen molecules July 4th, 2015

New Biosensor Produced in Iran to Detect Effective Drugs in Cancer Treatment July 4th, 2015

Clues to inner atomic life from subtle light-emission shifts: Hyperfine structure of light absorption by short-lived cadmium atom isotopes reveals characteristics of the nucleus that matter for high precision detection methods July 3rd, 2015

Groundbreaking research to help control liquids at micro and nano scales July 3rd, 2015

Announcements

A 'movie' of ultrafast rotating molecules at a hundred billion per second: A quantum wave-like nature was successfully observed in rotating nitrogen molecules July 4th, 2015

New Biosensor Produced in Iran to Detect Effective Drugs in Cancer Treatment July 4th, 2015

Clues to inner atomic life from subtle light-emission shifts: Hyperfine structure of light absorption by short-lived cadmium atom isotopes reveals characteristics of the nucleus that matter for high precision detection methods July 3rd, 2015

Pioneering Southampton scientist awarded prestigious physics medal July 3rd, 2015

Energy

New technology using silver may hold key to electronics advances July 2nd, 2015

Visible Light-Sensitive Photocatalysts Used for Purification of Contaminated Water in Iran June 30th, 2015

June 29th, 2015

Making new materials with micro-explosions: ANU media release: Scientists have made exotic new materials by creating laser-induced micro-explosions in silicon, the common computer chip material June 29th, 2015

Solar/Photovoltaic

Making new materials with micro-explosions: ANU media release: Scientists have made exotic new materials by creating laser-induced micro-explosions in silicon, the common computer chip material June 29th, 2015

Spain nanotechnology featured at NANO KOREA 2015 June 26th, 2015

Stanford researchers stretch a thin crystal to get better solar cells June 25th, 2015

Toward tiny, solar-powered sensors: New ultralow-power circuit improves efficiency of energy harvesting to more than 80 percent June 23rd, 2015

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