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.
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, firstname.lastname@example.org
Hongrui Jiang | EurekAlert!
Waste from paper and pulp industry supplies raw material for development of new redox flow batteries
12.10.2017 | Johannes Gutenberg-Universität Mainz
Low-cost battery from waste graphite
11.10.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research