New technique developed at MIT could enable a major boost in solar-cell efficiency

Home > Events > EE & RE Exhibition > News > • Branch News > New technique developed at MIT could enable a major boost in solar-cell efficiency

Show Pages

New technique developed at MIT could enable a major boost in solar-cell efficiency


David L. Chandler, MIT - 22.04.2013

Throughout decades of research on solar cells, one formula has been considered an absolute limit to the efficiency of such devices in converting sunlight into electricity: Called the Shockley-Queisser efficiency limit, it posits that the ultimate conversion efficiency can never exceed 34 percent for a single optimized semiconductor junction.

Now, researchers at MIT have shown that there is a way to blow past that limit as easily as today's jet fighters zoom through the sound barrier — which was also once seen as an ultimate limit.

Their work appears this week in a report in the journal Science, co-authored by graduate students including Daniel Congreve, Nicholas Thompson, Eric Hontz and Shane Yost, alumna Jiye Lee '12, and professors Marc Baldo and Troy Van Voorhis.

The principle behind the barrier-busting technique has been known theoretically since the 1960s, says Baldo, a professor of electrical engineering at MIT. But it was a somewhat obscure idea that nobody had succeeded in putting into practice. The MIT team was able, for the first time, to perform a successful "proof of principle" of the idea, which is known as singlet exciton fission. (An exciton is the excited state of a molecule after absorbing energy from a photon.)

In a standard photovoltaic (PV) cell, each photon knocks loose exactly one electron inside the PV material. That loose electron then can be harnessed through wires to provide an electrical current.

But in the new technique, each photon can instead knock two electrons loose. This makes the process much more efficient: In a standard cell, any excess energy carried by a photon is wasted as heat, whereas in the new system the extra energy goes into producing two electrons instead of one.

While others have previously "split" a photon's energy, they have done so using ultraviolet light, a relatively minor component of sunlight at Earth's surface. The new work represents the first time this feat has been accomplished with visible light, laying a pathway for practical applications in solar PV panels.

This was accomplished using an organic compound called pentacene in an organic solar cell. While that material's ability to produce two excitons from one photon had been known, nobody had previously been able to incorporate it within a PV device that generated more than one electron per photon.

"Our whole project was directed at showing that this splitting process was effective," says Baldo, who is also the director of the Center for Excitonics, sponsored by the U.S. Department of Energy. "We showed that we could get through that barrier."

The theoretical basis for this work was laid long ago, says Congreve, but nobody had been able to realize it in a real, functioning system. "In this system," he says, "everyone knew you could, they were just waiting for someone to do it."

"This is the landmark event we had all been waiting to see," adds Richard Friend, the Cavendish Professor of Physics at the University of Cambridge, who was not involved in this research. "This is really great research."

Since this was just a first proof of principle, the team has not yet optimized the energy-conversion efficiency of the system, which remains less than 2 percent. But ratcheting up that efficiency through further optimization should be a straightforward process, the researchers say. "There appears to be no fundamental barrier," Thompson says.

While today's commercial solar panels typically have an efficiency of at most 25 percent, a silicon solar cell harnessing singlet fission should make it feasible to achieve efficiency of more than 30 percent, Baldo says — a huge leap in a field typically marked by slow, incremental progress. In solar cell research, he notes, people are striving "for an increase of a tenth of a percent."

Solar panel efficiencies can also be improved by stacking different solar cells together, but combining solar cells is expensive with conventional solar-cell materials. The new technology instead promises to work as an inexpensive coating on solar cells.

The work made use of a known material, but the team is now exploring new materials that might perform the same trick even better. "The field is working on materials that were chanced upon," Baldo says — but now that the principles are better understood, researchers can begin exploring possible alternatives in a more systematic way.

The research was performed in the Center for Excitonics and supported by the U.S. Department of Energy. MIT has filed for a provisional patent on the technology.

Source: MIT

http://www.balkans.com/
 

 
 
Exhibitions & Conferences

Waste Management & Recycling

Sofia Sport & Healthy Life Exhibition

Via Expo is a Member of:


Bulgarian Association of Recycling


Bulgarian Photovoltaic Association


Bulgarian- Swiss Chamber of Commerce


German-Bulgarian Chamber of Industry and Commerce


Bulgarian Industrial Association

News


Adopting a Green Lifestyle

Prime:  prime Subtitle:  What values are implied by the word ‘green’? Images: I’ve always struggled with the word “green.” I’m not quite sure what “green building” means, but most definitions include the idea of environmental responsibility...
23/09/16|02:32 -- greenbuildingadvisor.com

TV Energy Labels May Be Misleading

Subtitle:  A study by the National Resource Defense Council claims manufacturers ‘exploit’ a loophole in government test procedures Images: Recently manufactured televisions could be using twice as much electricity as shown on government-required EnergyGuide labels as makers exploit a weakness in the Department of Energy's test procedures, the Natural Resource Defense Council says...
23/09/16|12:12 -- greenbuildingadvisor.com

EUR 150 Mio support for a biomass and waste-fired cogeneration plant in Lithuania approved by the EC

The state owned energy group of Lithuania is building a EUR 345 million biomass and waste-fired...
19/09/16|04:40 -- enercee.net

Nevada Solar Customers Win a Round

Subtitle:  Customers who have already installed photovoltaic (PV) systems will keep full retail net metering Images: Homeowners in Nevada with photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow...
19/09/16|03:54 -- greenbuildingadvisor.com

Georgia City Bucks Wood High-Rise Trend

Subtitle:  In Sandy Springs, Georgia, wood structural components won't be allowed in large buildings over three stories tall Images: For some builders and architects, wood is the building material of the future, with lower costs and less embodied energyEnergy that goes into making a product; includes energy required for growth, extraction, and transportation of the raw material as well as manufacture, packaging, and transportation of the finished product...
16/09/16|04:27 -- greenbuildingadvisor.com

Indoor Microbes and Human Health

Prime:  prime Subtitle:  How do the bacteria and fungi living in our homes affect our health? Images: The word “health” is usually reserved for living things. Our children can be healthy or unhealthy, and so can our pets and the apple trees in the back yard...
16/09/16|02:29 -- greenbuildingadvisor.com

GE Will Drop Heat-Pump Water Heaters

Subtitle:  After a 2012 launch, sales prove disappointing despite efficiencies much higher than conventional electric units Images: Improved energy efficiency, utility incentives, and a federal tax credit aren't going to be enough to save GE's GeoSpring heat-pump water heaterAn appliance that uses an air-source heat pump to heat domestic hot water...
14/09/16|12:38 -- greenbuildingadvisor.com

A Web-Based Information Resource From the DOE

Prime:  prime Subtitle:  The Building America Solution Center aims to be a one-stop information library for energy-conscious builders Images: The Building America program, a branch of the U...
09/09/16|02:15 -- greenbuildingadvisor.com

 

 

2016 edition
was realized under
the patronage of:

 

With the Support of:

 

Media Sponsor:

 

Official Media Partner:

 

Official Hotel:

ViaExpo