Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > New Path To Solar Energy Via Solid-State Photovoltaics

These nanoscale images of bismuth ferrite thin films show ordered arrays of 71 degree domain walls (top) and 109 degree doman walls (bottom). By changing the polarization direction of the bismuth ferrite, these domain walls give rise to the photovoltaic effect. (Image from Seidel, et. al.)
These nanoscale images of bismuth ferrite thin films show ordered arrays of 71 degree domain walls (top) and 109 degree doman walls (bottom). By changing the polarization direction of the bismuth ferrite, these domain walls give rise to the photovoltaic effect. (Image from Seidel, et. al.)

Abstract:
A newly discovered path for the conversion of sunlight to electricity could brighten the future for photovoltaic technology. Researchers with Lawrence Berkeley National Laboratory (Berkeley Lab) have found a new mechanism by which the photovoltaic effect can take place in semiconductor thin-films. This new route to energy production overcomes the bandgap voltage limitation that continues to plague conventional solid-state solar cells.

New Path To Solar Energy Via Solid-State Photovoltaics

Berkeley, CA | Posted on March 31st, 2010

Working with bismuth ferrite, a ceramic made from bismuth, iron and oxygen that is multiferroic - meaning it simultaneously displays both ferroelectric and ferromagnetic properties - the researchers discovered that the photovoltaic effect can spontaneously arise at the nanoscale as a result of the ceramic's rhombohedrally distorted crystal structure. Furthermore, they demonstrated that the application of an electric field makes it possible to manipulate this crystal structure and thereby control photovoltaic properties.

"We're excited to find functionality that has not been seen before at the nanoscale in a multiferroic material," said Jan Seidel, a physicist who holds joint appointments with Berkeley Lab's Materials Sciences Division and the UC Berkeley Physics Department. "We're now working on transferring this concept to higher efficiency energy-research related devices."

Seidel is one of the lead authors of a paper in the journal Nature Nanotechnology that describes this work titled, "Above-bandgap voltages from ferroelectric photovoltaic devices." Co-authoring this paper with Seidel were Seung-Yeul Yang, Steven Byrnes, Padraic Shafer,Chan-Ho Yang, Marta Rossell, Pu Yu, Ying-Hao Chu, James Scott, Joel Ager, Lane Martin and Ramamoorthy Ramesh.

At the heart of conventional solid-state solar cells is a p-n junction, the interface between a semiconductor layer with an abundance of positively-charged "holes," and a layer with an abundance of negatively charged electrons. When photons from the sun are absorbed, their energy creates electron-hole pairs that can be separated within a "depletion zone," a microscopic region at the p-n junction measuring only a couple of micrometers across, then collected as electricity. For this process to take place, however, the photons have to penetrate the material to the depletion zone and their energy has to precisely match the energy of the semiconductor's electronic bandgap - the gap between its valence and conduction energy bands where no electron states can exist.

"The maximum voltage conventional solid-state photovoltaic devices can produce is equal to the energy of their electronic bandgap," Seidel says. "Even for so called tandem-cells, in which several semiconductor p-n junctions are stacked, photovoltages are still limited because of the finite penetration depth of light into the material."

Working through Berkeley Lab's Helios Solar Energy Research Center, Seidel and his collaborators discovered that by applying white light to bismuth ferrite, a material that is both ferroelectric and antiferromagnetic, they could generate photovoltages within submicroscopic areas between one and two nanometers across. These photovoltages were significantly higher than bismuth ferrite's electronic bandgap.

"The bandgap energy of the bismuth ferrite is equivalent to 2.7 volts. From our measurements we know that with our mechanism we can get approximately 16 volts over a distance of 200 microns. Furthermore, this voltage is in principle linear scalable, which means that larger distances should lead to higher voltages."

Behind this new mechanism for photovoltage generation are domain walls - two-dimensional sheets that run through a multiferroic and serve as transition zones, separating regions of different ferromagnetic or ferroelectric properties. In their study, Seidel and his collaborators found that these domain walls can serve the same electron-hole separation purpose as depletion zones only with distinct advantages.

"The much smaller scale of these domain walls enables a great many of them to be stacked laterally (sideways) and still be reached by light," Seidel says. "This in turn makes it possible to increase the photovoltage values well above the electronic bandgap of the material."

The photovoltaic effect arises because at the domain walls the polarization direction of the bismuth ferrite changes, which leads to steps in the electrostatic potential. Through annealing treatments of the substrate upon which bismuth ferrite is grown, the material's rhombohedral crystals can be induced to form domain walls that change the direction of electric field polarization by either 71, 109 or 180 degrees. Seidel and his collaborators measured the photovoltages created by the 71 and 109 degree domain walls.

"The 71 degree domain walls showed unidirectional in-plane polarization alignment and produced an aligned series of potential voltage steps," Seidel says. "Although the potential step at the 109 degree domain was higher than the 71 degree domain, it showed two variants of the in-plane polarization which ran in opposite directions."

Seidel and his colleagues were also able to use a 200 volt electric pulse to either reverse the polarity of the photovoltaic effect or turn it off altogether. Such controllability of the photovoltaic effect has never been reported in conventional photovoltaic systems, and it paves the way for new applications in nano-optics and nano-electronics.

"While we have not yet demonstrated these possible new applications and devices, we believe that our research will stimulate concepts and thoughts that are based on this new direction for the photovoltaic effect," Seidel says.

Additional Information

For more information on the Helios Solar Energy Research Center, visit the Website at www.lbl.gov/LBL-Programs/helios-serc/index.html

####

About Berkeley Lab
Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California. Visit our website at www.lbl.gov.

For more information, please click here

Contacts:
Lynn Yarris
(510) 486-5375

Copyright © Berkeley Lab

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

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Leti Develops Proof of Concept to Test Wireless Systems in Aircraft: Will Present Results of Joint Project at AeroTech Conference And Exhibition in Fort Worth, Texas, Sept. 26-28 September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

A new approach to ultrafast light pulses: Unusual fluorescent materials could be used for rapid light-based communications systems September 19th, 2017

Thin films

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

Thinking thin brings new layering and thermal abilities to the semiconductor industry: In a breakthrough for the semiconductor industry, researchers demonstrate a new layer transfer technique called "controlled spalling" that creates many thin layers from a single gallium nitride July 11th, 2017

Possible Futures

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Leti Develops Proof of Concept to Test Wireless Systems in Aircraft: Will Present Results of Joint Project at AeroTech Conference And Exhibition in Fort Worth, Texas, Sept. 26-28 September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

A new approach to ultrafast light pulses: Unusual fluorescent materials could be used for rapid light-based communications systems September 19th, 2017

Nanoelectronics

Bit data goes anti-skyrmions September 1st, 2017

Ames Laboratory scientists move graphene closer to transistor applications August 30th, 2017

GLOBALFOUNDRIES Demonstrates 2.5D High-Bandwidth Memory Solution for Data Center, Networking, and Cloud Applications: Solution leverages 2.5D packaging with low-latency, high-bandwidth memory PHY built on FX-14™ ASIC design system August 9th, 2017

GLOBALFOUNDRIES, Silicon Mobility Deliver the Industry’s First Automotive FPCU to Boost Performance for Hybrid and Electric Vehicles: Silicon Mobility and GF’s 55nm LPx -enabled platform, with SST’s highly-reliable SuperFlash® memory technology, boosts automotive performance, ene August 3rd, 2017

Discoveries

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

A new approach to ultrafast light pulses: Unusual fluorescent materials could be used for rapid light-based communications systems September 19th, 2017

New quantum phenomena in graphene superlattices September 18th, 2017

Announcements

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Leti Develops Proof of Concept to Test Wireless Systems in Aircraft: Will Present Results of Joint Project at AeroTech Conference And Exhibition in Fort Worth, Texas, Sept. 26-28 September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

A new approach to ultrafast light pulses: Unusual fluorescent materials could be used for rapid light-based communications systems September 19th, 2017

Energy

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

Insect eyes inspire new solar cell design from Stanford August 31st, 2017

The power of perovskite: OIST researchers improve perovskite-based technology in the entire energy cycle, from solar cells harnessing power to LED diodes to light the screens of future electronic devices and other lighting applications August 18th, 2017

Photonics/Optics/Lasers

A new approach to ultrafast light pulses: Unusual fluorescent materials could be used for rapid light-based communications systems September 19th, 2017

Graphene based terahertz absorbers: Printable graphene inks enable ultrafast lasers in the terahertz range September 13th, 2017

First on-chip nanoscale optical quantum memory developed: Smallest-yet optical quantum memory device is a storage medium for optical quantum networks with the potential to be scaled up for commercial use September 11th, 2017

High-speed quantum memory for photons September 9th, 2017

Solar/Photovoltaic

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

Hydrogen power moves a step closer: Physicists are developing methods of creating renewable fuel from water using quantum technology September 15th, 2017

Insect eyes inspire new solar cell design from Stanford August 31st, 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