Nanotechnology Now





Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > A New Twist for Nanopillar Light Collectors

On the left a schematic of a germanium nanopillar array embedded in an alumina foil membrane; on the right are cross-sectional SEM images of a blank alumina membrane with dual-diameter pores; inset shows germanium nanopillars after growth. (Images courtesy of Ali Javey)
On the left a schematic of a germanium nanopillar array embedded in an alumina foil membrane; on the right are cross-sectional SEM images of a blank alumina membrane with dual-diameter pores; inset shows germanium nanopillars after growth. (Images courtesy of Ali Javey)

Abstract:
The nanopillar story has taken a new twist and the future for these materials now looks brighter than ever.

A New Twist for Nanopillar Light Collectors

Berkeley, CA | Posted on November 17th, 2010

Sunlight represents the cleanest, greenest and far and away most abundant of all energy sources, and yet its potential remains woefully under-utilized. High costs have been a major deterrant to the large-scale applications of silicon-based solar cells. Nanopillars - densely packed nanoscale arrays of optically active semiconductors - have shown potential for providing a next generation of relatively cheap and scalable solar cells, but have been hampered by efficiency issues. The nanopillar story, however, has taken a new twist and the future for these materials now looks brighter than ever.

"By tuning the shape and geometry of highly ordered nanopillar arrays of germanium or cadmium sulfide, we have been able to drastically enhance the optical absorption properties of our nanopillars," says Ali Javey, a chemist who holds joint appointments with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley.

Javey, a faculty scientist with Berkeley Lab's Materials Sciences Division and a UC Berkeley professor of electrical engineering and computer science, has been at the forefront of nanopillar research. He and his group were the first to demonstrate a technique by which cadmium sulfide nanopillars can be mass-produced in large-scale flexible modules. In this latest work, they were able to produce nanopillars that absorb light as well or even better than commercial thin-film solar cells, using far less semiconductor material and without the need for anti-reflective coating.

"To enhance the broad-band optical absorption efficiency of our nanopillars we used a novel dual-diameter structure that features a small (60 nanometers) diameter tip with minimal reflectance to allow more light in, and a large (130 nanometers) diameter base for maximal absorbtion to enable more light to be converted into electricity," Javey says. "This dual-diameter structure absorbed 99-percent of incident visible light, compared to the 85 percent absorbtion by our earlier nanopillars, which had the same diameter along their entire length."

Theoretical and experimental works have shown that 3-D arrays of semiconductor nanopillars - with well-defined diameter, length and pitch - excel at trapping light while using less than half the semiconductor material required for thin-film solar cells made of compound semiconductors, such as cadmium telluride, and about one-percent of the material used in solar cells made from bulk silicon. But until the work of Javey and his research group, fabricating such nanopillars was a complex and cumbersome procedure.

Javey and his colleagues fashioned their dual diameter nanopillars from molds they made in 2.5 millimeter-thick alumina foil. A two-step anodization process was used to create an array of one micrometer deep pores in the mold with dual diameters - narrow at the top and broad at the bottom. Gold particles were then deposited into the pores to catalyze the growth of the semiconductor nanopillars.

"This process enables fine control over geometry and shape of the single-crystalline nanopillar arrays, without the use of complex epitaxial and/or lithographic processes," Javey says. "At a height of only two microns, our nanopillar arrays were able to absorb 99-percent of all photons ranging in wavelengths between 300 to 900 nanometers, without having to rely on any anti-reflective coatings."

The germanium nanopillars can be tuned to absorb infrared photons for highly sensitive detectors, and the cadmium sulfide/telluride nanopillars are ideal for solar cells. The fabrication technique is so highly generic, Javey says, it could be used with numerous other semiconductor materials as well for specific applications. Recently, he and his group demonstrated that the cross-sectional portion of the nanopillar arrays can also be tuned to assume specific shapes - square, rectangle or circle - simply by changing the shape of the template.

"This presents yet another degree of control in the optical absorption properties of nanopillars," Javey says.

Javey's dual-diameter nanopillar research was partially funded through the National Science Foundation's Center of Integrated Nanomechanical Systems (COINS) and through Berkeley Lab LDRD funds.

A paper describing this research appears on-line in the journal NANO Letters under the title "Ordered Arrays of Dual-Diameter Nanopillars for Maximized Optical Absorption." Co-authoring the paper with Javey were Zhiyong Fan, Rehan Kapadia, Paul Leu,Xiaobo Zhang, Yu-Lun Chueh, Kuniharu Takei, Kyoungsik Yu, Arash Jamshidi, Asghar Rathore, Daniel Ruebusch and Ming Wu.

For more about the research of Ali Javey, visit his Website at nano.eecs.berkeley.edu

####

About Berkeley Lab
Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research for DOE’s Office of Science 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

Superconductor could be realized in a broken Lorenz invariant theory July 7th, 2015

New technique enables magnetic patterns to be mapped in 3-D July 7th, 2015

Crystal structure and magnetism -- new insight into the fundamentals of solid state physics: HZB team decodes relationship between magnetic interactions and the distortions in crystal structure within a geometrically 'frustrated' spinel system July 7th, 2015

Down to the quantum dot: Jülich researchers develop ultrahigh-resolution 3-D microscopy technique for electric fields July 7th, 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

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

World’s 1st Full-Color, Flexible, Skin-Like Display Developed at UCF June 24th, 2015

Picosun ALD breaks through in medical technology June 23rd, 2015

Govt.-Legislation/Regulation/Funding/Policy

A cool way to form 2-D conducting polymers using ice: POSTECH scientists develop breakthrough technique to easily optimize electrical properties of Polyaniline nanosheets to an unprecedented level in an environmental-friendly and inexpensive way July 7th, 2015

New technique enables magnetic patterns to be mapped in 3-D July 7th, 2015

Surfing a wake of light: Researchers observe and control light wakes for the first time July 6th, 2015

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

Possible Futures

BBC World Service to broadcast Forum discussion on graphene July 6th, 2015

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

Harris & Harris Group Portfolio Company D-Wave Systems Announces 1,000 Qubit Processor and is Discussed in the Economist June 23rd, 2015

Global Nanoclays Market Analysis, Size, Growth, Trends And Segment Forecasts, 2015 To 2022: Grand View Research, Inc June 15th, 2015

Academic/Education

Oxford Instruments’ TritonXL Cryofree dilution refrigerator selected for the Oxford NQIT Quantum Technology Hub project June 30th, 2015

Rice University boots up powerful microscopes: New electron microscopes will capture images at subnanometer resolution June 29th, 2015

Six top Catalan research centres constitute ‘The Barcelona Institute of Science and Technology’ to pursue a joint scientific endeavour June 27th, 2015

Lancaster University revolutionary quantum technology research receives funding boost June 22nd, 2015

Announcements

Superconductor could be realized in a broken Lorenz invariant theory July 7th, 2015

New technique enables magnetic patterns to be mapped in 3-D July 7th, 2015

Crystal structure and magnetism -- new insight into the fundamentals of solid state physics: HZB team decodes relationship between magnetic interactions and the distortions in crystal structure within a geometrically 'frustrated' spinel system July 7th, 2015

Down to the quantum dot: Jülich researchers develop ultrahigh-resolution 3-D microscopy technique for electric fields July 7th, 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