Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

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

CubeSat Structures Competition Opens Space Design to Students of the World December 16th, 2017

Record high photoconductivity for new metal-organic framework material December 15th, 2017

Error-free into the quantum computer age December 15th, 2017

Leti Will Demonstrate First 3D Anti-Crash Solution for Embedding in Drones: Fitted on a Mass-Market Microcontroller, 360Fusion Software Technology Detects any Dynamic Obstacle and Helps Guide Drones Away from Collisions December 15th, 2017

Videos/Movies

Quantum memory with record-breaking capacity based on laser-cooled atoms December 15th, 2017

Thin films

MIPT scientists revisit optical constants of ultrathin gold films October 20th, 2017

Rice University chemists make laser-induced graphene from wood July 31st, 2017

Graduate Students from Across the Country Attend Hands-on NanoCamp: Prominent scientists Warren Oliver, Ph.D., and George Pharr, Ph.D., presented a weeklong NanoCamp for hand-picked graduate students across the United States July 26th, 2017

Studying Argon Gas Trapped in Two-Dimensional Array of Tiny "Cages": Understanding how individual atoms enter and exit the nanoporous frameworks could help scientists design new materials for gas separation and nuclear waste remediation July 17th, 2017

Discoveries

Quantum memory with record-breaking capacity based on laser-cooled atoms December 15th, 2017

Record high photoconductivity for new metal-organic framework material December 15th, 2017

Error-free into the quantum computer age December 15th, 2017

Synthetic protein packages its own genetic material and evolves computationally designed protein assemblies are advancing research in synthetic life and in targeted drug delivery December 15th, 2017

Announcements

CubeSat Structures Competition Opens Space Design to Students of the World December 16th, 2017

Record high photoconductivity for new metal-organic framework material December 15th, 2017

Error-free into the quantum computer age December 15th, 2017

Leti Will Demonstrate First 3D Anti-Crash Solution for Embedding in Drones: Fitted on a Mass-Market Microcontroller, 360Fusion Software Technology Detects any Dynamic Obstacle and Helps Guide Drones Away from Collisions December 15th, 2017

Energy

Inorganic-organic halide perovskites for new photovoltaic technology November 6th, 2017

Dendritic fibrous nanosilica: all-in-one nanomaterial for energy, environment and health November 4th, 2017

New nanomaterial can extract hydrogen fuel from seawater: Hybrid material converts more sunlight and can weather seawater's harsh conditions October 4th, 2017

Researchers set time limit for ultrafast perovskite solar cells September 22nd, 2017

Solar/Photovoltaic

Record high photoconductivity for new metal-organic framework material December 15th, 2017

Inorganic-organic halide perovskites for new photovoltaic technology November 6th, 2017

New nanomaterial can extract hydrogen fuel from seawater: Hybrid material converts more sunlight and can weather seawater's harsh conditions October 4th, 2017

Researchers set time limit for ultrafast perovskite solar cells September 22nd, 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