Subscribe free to our newsletters via your
  Solar Energy News  




Subscribe free to our newsletters via your




















SOLAR DAILY
A New Way to Image Solar Cells in 3-D
by Staff Writers
Berkeley CA (SPX) Nov 16, 2016


The Molecular Foundry's Edward Barnard is part of a team of scientists that developed a new way to see inside solar cells. Image courtesy Marilyn Chung.

Next-generation solar cells made of super-thin films of semiconducting material hold promise because they're relatively inexpensive and flexible enough to be applied just about anywhere. Researchers are working to dramatically increase the efficiency at which thin-film solar cells convert sunlight to electricity. But it's a tough challenge, partly because a solar cell's subsurface realm-where much of the energy-conversion action happens-is inaccessible to real-time, nondestructive imaging. It's difficult to improve processes you can't see.

Now, scientists from the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a way to use optical microscopy to map thin-film solar cells in 3-D as they absorb photons.

The method, reported Nov. 15 in the journal Advanced Materials, was developed at the Molecular Foundry, a DOE Office of Science user facility located at Berkeley Lab. It images optoelectronic dynamics in materials at the micron scale, or much thinner than the diameter of a human hair. This is small enough to see individual grain boundaries, substrate interfaces, and other internal obstacles that can trap excited electrons and prevent them from reaching an electrode, which saps a solar cell's efficiency.

So far, scientists have used the technique to better understand why adding a specific chemical to solar cells made of cadmium telluride (CdTe)-the most common thin-film material-improves the solar cells' performance.

"To make big gains in photovoltaic efficiency, we need to see what's happening throughout a working photovoltaic material at the micron scale, both on the surface and below, and our new approach allows us to do that," says Edward Barnard, a principal scientific engineering associate at the Molecular Foundry. He led the effort with James Schuck, the director of the Imaging and Manipulation of Nanostructures facility at the Molecular Foundry.

The imaging method is born out of a collaboration between Molecular Foundry scientists and Foundry users from PLANT PV Inc., an Alameda, California-based company. While fabricating new solar cell materials at the Molecular Foundry, the team found that standard optical techniques couldn't image the inner-workings of the materials, so they developed the new technique to obtain this view. Next, scientists from the National Renewable Energy Laboratory came to the Molecular Foundry and used the new method to study CdTe solar cells.

To develop the approach, the scientists modified a technique called two-photon microscopy (which is used by biologists to see inside thick samples such as living tissue) so that it can be applied to bulk semiconductor materials.

The method uses a highly focused laser beam of infrared photons that penetrate inside the photovoltaic material. When two low-energy photons converge at the same pinpoint, there's enough energy to excite electrons. These electrons can be tracked to see how long they last in their excited state, with long-lifetime electrons appearing as bright spots in microscopy images. In a solar cell, long-lifetime electrons are more likely to reach an electrode.

In addition, the laser beam can be systematically repositioned throughout a test-sized solar cell, creating a 3-D map of a solar cell's entire optoelectronic dynamics.

The method has already shed light on the benefits of treating CdTe solar cells with cadmium chloride, which is often added during the fabrication process.

Scientists know cadmium chloride improves the efficiency of CdTe solar cells, but its effect on excited electrons at the micron scale is not well understood. Studies have shown that the chlorine ions tend to pile up at grain boundaries, but how this changes the lifetime of excited electrons is unclear.

Thanks to the new imaging technique, the researchers discovered the cadmium chloride treatment increases the lifetime of excited electrons at the grain boundaries, as well as within the grains themselves. This is easily seen in 3-D images of CdTe solar cells with and without the treatment. The treated solar cell "lights up" much more uniformly throughout the material, both in the grains and the spaces in between.

"Scientists have known that cadmium chloride passivation improves the lifetime of electrons in CdTe cells, but now we've mapped at the micron scale where this improvement occurs," says Barnard.

The new imaging technique could help scientists make more informed decisions about improving a host of thin-film solar cell materials in addition to CdTe, such as perovskite and organic compounds.

"Researchers trying to push photovoltaic efficiency could use our technique to see if their strategies are working at the microscale, which will help them design better test-scale solar cells-and eventually full-sized solar cells for rooftops and other real-world applications," he says.

The research was supported by the Department of Energy's Office of Science and by a SunShot Initiative award from the Office of Energy Efficiency and Renewable Energy.


Comment on this article using your Disqus, Facebook, Google or Twitter login.

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Berkeley Lab
All About Solar Energy at SolarDaily.com






Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
SOLAR DAILY
Solar industry shift tactics to sell more solar AC and smart modules
London, UK (SPX) Nov 14, 2016
The business model of microinverter and power optimizer suppliers is set to shift from standalone units to integrated systems, such as Smart and AC modules, according to new analysis released today by IHS Markit. The annual IHS Technology PV Microinverter and Power Optimizer Report examines market size, pricing and vendor market share. It forecasts revenue for Smart and AC modules will jump from ... read more


SOLAR DAILY
Bioelectronics at the speed of life

NREL finds bacterium that uses both CO2 and cellulose to make biofuels

State partnerships can promote increased bio-energy production, reduce emissions

Turning biofuel waste into wealth in a single step

SOLAR DAILY
Crowd workers help robot keep conversation fresh

Artificial-intelligence system surfs web to improve its performance

Chemists develop world's first light-seeking synthetic Nanorobot

'Bots' step up for 2016 election news coverage

SOLAR DAILY
Microsoft Corp. taps deeper into wind power

Interior set to rule on future of BLM's Renewable Energy Program

Alberta pushing hard on renewable energy pedal

Cuomo announces major progress in offshore wind development

SOLAR DAILY
VW reaches 3.0-liter diesel agreement with EPA: report

Samsung to buy US auto parts supplier Harman for $8 bn

China auto sales growth falls back in October: group

VW's Audi hit with fresh emissions cheating lawsuit

SOLAR DAILY
First observations of tongue deformation of plasma

Battery cars a better choice for reducing emissions than fuel cells

Bottlebrush polymers make dielectric elastomers viable for use in devices

PPPL physicists build diagnostic that measures plasma velocity in real time

SOLAR DAILY
Time to tackle the UK's plutonium mountain

Vietnam to scrap planned nuclear plants: state media

Japan, India sign controversial civil nuclear deal

French, Finns divided over nuclear dispute ruling

SOLAR DAILY
Study: LED lights draw fewer insects

Shifting focus leaves mixed bag for German utility RWE

Deeper carbon cuts needed to avoid climate tragedy: UN

New program makes energy-harvesting computers more reliable

SOLAR DAILY
Mangrove protection key to survival for Senegalese community

Morocco's oases fight back creeping desert sands

Database captures most extensive urban tree sizes, growth rates across United States

New warning over spread of ash dieback




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement