Nav: Home

Tiny high-performance solar cells turn power generation sideways

August 03, 2016

MADISON, Wis. -- University of Wisconsin-Madison engineers have created high-performance, micro-scale solar cells that outshine comparable devices in key performance measures. The miniature solar panels could power myriad personal devices -- wearable medical sensors, smartwatches, even autofocusing contact lenses.

Large, rooftop photovoltaic arrays generate electricity from charges moving vertically. The new, small cells, described today (Aug. 3, 2016) in the journal Advanced Materials Technologies, capture current from charges moving side-to-side, or laterally. And they generate significantly more energy than other sideways solar systems.

New-generation lateral solar cells promise to be the next big thing for compact devices because arranging electrodes horizontally allows engineers to sidestep a traditional solar cell fabrication process: the arduous task of perfectly aligning multiple layers of the cell's material atop one another.

"From a fabrication point of view, it is always going to be easier to make side-by-side structures," says Hongrui Jiang, a UW-Madison professor of electrical and computer engineering and corresponding author on the paper. "Top-down structures need to be made in multiple steps and then aligned, which is very challenging at small scales."

Lateral solar cells also offer engineers greater flexibility in materials selection.

Top-down photovoltaic cells are made up of two electrodes surrounding a semiconducting material like slices of bread around the meat in a sandwich. When light hits the top slice, charge travels through the filling to the bottom layer and creates electric current.

In the top-down arrangement, one layer needs to do two jobs: It must let in light and transmit charge. Therefore, the material for one electrode in a typical solar cell must be not only highly transparent, but also electrically conductive. And very few substances perform both tasks well.

Instead of building its solar cell sandwich one layer at a time, Jiang's group created a densely packed, side-by-side array of miniature electrodes on top of transparent glass. The resulting structure -- akin to an entire loaf of bread's worth of solar-cell sandwiches standing up sideways on a clear plate -- separates light-harvesting and charge-conducting functions between the two components.

Generally, synthesizing such sideways sandwiches is no simple matter. Other approaches that rely on complicated internal nanowires or expensive materials called perovskites fall short on multiple measures of solar cell quality.

"We easily beat all of the other lateral structures," says Jiang.

Existing top-of the-line lateral new-generation solar cells convert merely 1.8 percent of incoming light into useful electricity. Jiang's group nearly tripled that measure, achieving up to 5.2 percent efficiency.

"In other structures, a lot of volume goes wasted because there are no electrodes or the electrodes are mismatched," says Jiang. "The technology we developed allows us to make very compact lateral structures that take advantage of the full volume."

Packing so many electrodes into such a small volume boosted the devices' "fill factors," a metric related to the maximum attainable power, voltage and current. The structures realized fill factors up to 0.6 -- more than twice the demonstrated maximum for other lateral new-generation solar cells.

Jiang and colleagues are working to make their solar cells even smaller and more efficient by exploring materials that further optimize transparency and conductivity. Ultimately they plan to develop a small-scale, flexible solar cell that could provide power to an electrically tunable contact lens.
-end-
Other authors on the paper included Xi Zhang, Yinggang Huang, Hao Bian, Hewei Liu, and Xuezhen Huang. The National Institutes of Health provided funding for the research.

Sam Million-Weaver, perspective@engr.wisc.edu

University of Wisconsin-Madison

Related Solar Cells Articles:

Solar cells with new interfaces
Scientists from NUST MISIS (Russia) and University of Rome Tor Vergata found out that a microscopic quantity of two-dimensional titanium carbide called MXene significantly improves collection of electrical charges in a perovskite solar cell, increasing the final efficiency above 20%.
Welcome indoors, solar cells
Swedish and Chinese scientists have developed organic solar cells optimised to convert ambient indoor light to electricity.
Mapping the energetic landscape of solar cells
A new spectroscopic method now makes it possible to measure and visualize the energetic landscape inside solar cells based on organic materials.
Solar energy becomes biofuel without solar cells
Soon we will be able to replace fossil fuels with a carbon-neutral product created from solar energy, carbon dioxide and water.
A good first step toward nontoxic solar cells
A team of engineers at Washington University in St. Louis has found what they believe is a more stable, less toxic semiconductor for solar applications, using a novel double mineral discovered through data analytics and quantum-mechanical calculations.
Organic solar cells will last 10 years in space
Scientists from the Skoltech Center for Energy Science and Technology, the Institute for Problems of Chemical Physics of RAS, and the Department of Chemistry of MSU presented solar cells based on conjugated polymers and fullerene derivatives, that demonstrated record-high radiation stability and withstand gamma radiation of >6,000 Gy raising hopes for their stable operation on the near-earth orbit during 10 years or even longer.
Next-gen solar cells spin in new direction
A nanomaterial made from phosphorus, known as phosphorene, is shaping up as a key ingredient for more sustainable and efficient next-generation perovskite solar cells.
Caffeine gives solar cells an energy boost
Scientists from the University of California, Los Angeles (UCLA) and Solargiga Energy in China have discovered that caffeine can help make a promising alternative to traditional solar cells more efficient at converting light to electricity.
New properties of perovskite solar cells
Perovskite solar cells are lighter and cheaper than silicon, their production is non-toxic.
Making solar cells is like buttering bread
Formamidinium lead iodide is a very good material for photovoltaic cells, but getting the correct and stable crystal structure is a challenge.
More Solar Cells News and Solar Cells Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.