Interesting Article

EmptyKube's picture

Okay...copied from the email I sent the group....Smiling

Web Site: ScienceDaily Magazine
Page URL:


Original Source: Princeton University
Date Posted: 2003-09-12

New Technique Could Lead To Widespread Use Of Solar Power; Researchers Envision Mass-produced Rolls Of Material That Converts Sunlight To Electricity
Princeton electrical engineers have invented a technique for making solar cells that, when combined with other recent advances, could yield a highly economical source of energy.

The results, reported in the Sept. 11 issue of Nature, move scientists closer to making a new class of solar cells that are not as efficient as conventional ones, but could be vastly less expensive and more versatile. Solar cells, or photovoltaics, convert light to electricity and are used to power many devices, from calculators to satellites.

The new photovoltaics are made from "organic" materials, which consist of small carbon-containing molecules, as opposed to the conventional inorganic, silicon-based materials. The materials are ultra-thin and flexible and could be applied to large surfaces.

Organic solar cells could be manufactured in a process something like printing or spraying the materials onto a roll of plastic, said Peter Peumans, a graduate student in the lab of electrical engineering professor Stephen Forrest. "In the end, you would have a sheet of solar cells that you just unroll and put on a roof," he said.

Peumans and Forrest cowrote the paper in collaboration with Soichi Uchida, a researcher visiting Princeton from Nippon Oil Co.

The cells also could be made in different colors, making them attractive architectural elements, Peumans said. Or they could be transparent so they could be applied to windows. The cells would serve as tinting, letting half the light through and using the other half to generate power, he said.

Because of these qualities, researchers have pursued organic photovoltaic films for many years, but have been plagued with problems of efficiency, said Forrest. The first organic solar cell, developed in 1986, was 1 percent efficient -- that is, it converted only 1 percent of the available light energy into electrical energy. "And that number stood for about 15 years," said Forrest.

Forrest and colleagues recently broke that barrier by changing the organic compounds used to make their solar cells, yielding devices with efficiencies of more than 3 percent. The most recent advance reported in Nature involves a new method for forming the organic film, which increased the efficiency by 50 percent.

Researchers in Forrest's lab are now planning to combine the new materials and techniques. Doing so could yield at least 5 percent efficiency, which would make the technology attractive to commercial manufacturers. With further commercial development, organic solar devices would be viable in the marketplace with 5 to 10 percent efficiency, the researchers estimated. "We think we have pathway for using this and other tricks to get to 10 percent reasonably quickly," Forrest said.

By comparison, conventional silicon chip-based solar cells are about 24 percent efficient. "Organic solar cells will be cheaper to make, so in the end the cost of a watt of electricity will be lower than that of conventional materials," said Peumans.

The technique the researchers discovered also opens new areas of materials science that could be applied to other types of technology, the researchers said. Solar cells are made of two types of materials sandwiched together, one that gives up electrons and another that attracts them, allowing a flow of electricity. The Princeton researchers figured out how to make those two materials mesh together like interlocking fingers so there is more opportunity for the electrons to transfer.

The key to this advance was to apply a metal cap to the film of material as it is being made. The cap allowed the surface of the material to stay smooth and uniform while the internal microstructure changed and meshed together, which was an unexpected result, said Forrest. The researchers then developed a mathematical model to explain the behavior, which will likely prove useful in creating other micromaterials, Forrest said.

"We've shown a very new and general process for reorganizing the morphology of materials and that was really unanticipated," Forrest said.

The research was supported by grants from the Air Force Office of Scientific Research, the National Renewable Energy Laboratory and the Global Photonic Energy Corp.


Note: This story has been adapted from a news release issued by Princeton University.

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Re:Interesting Article

Thanks for the clipping, Mike. I do like to stay abreast of developments in solar energy. I hope this isn't one of those "breakthroughs" that comes and goes.

To err is human. I am not human.

EmptyKube's picture

Re:Interesting Article

I like the idea of being able to buy "rolls" of solar cells, or spray painting them on. Both ideas are in tune with the idea of flexible media for displaying graphics. The fact that a single cell only gets a 5% conversion (meaning only 5% of the light hitting the cell becomes electricity) at first still seemed low to me, until I started thinking about the idea of "rolls"...cover enough surface area, and that 5% isn't bad at all.

Re:Interesting Article

I'm in Rome atm (business trip) and I'm working with a: Russian Jew living in Italy with family in Israel, who speaks Russian, Italian, Hebrew, and English. He is married to a Moroccan muslim (!) who speaks Italian and French, and maybe more.

Anyway, he tells me Israelis heat their homes and water with solar power, and have done so for years. His father has a solar cell on his roof, and it has been so long since he has done any maintenance to it that he doesn't remember where it is.

This makes sense, really: Israel is a technically advanced country with a severe lack of space and resources. They also get a lot of sunlight. So they will eat the initial expense of putting solar cells on their roofs to save the money and inconvenience of fossil fuels in the long run.

In North America, with some of the lowest fossil fuels costs in the world, there would be less encouragement to use alternative sources. And solar power isn't an option everywhere -- it takes a lot of space and requires regular sunlight.

For example, in Canada, heat pumps are becoming more popular in remote areas. They take heat from deep inside the earth and bring it to the surface. They are expensive to put in, but dirt cheap (hahaha) to run. People in cities aren't putting them in though, because natural gas is cheap for them.

Rooftops aren't an ideal solution either. People do other things with rooftops, like antennas, gardens, pigeon coops, etc. However, if a rooftop isn't being used for anything else, and solar cells are cheap, people may be willing to fork over the initial expense for long term gain.

Here's another thought: in Japan, people are getting tax breaks to put in rooftop gardens. Why? For reducing heat pollution. The heat emitted from Tokyo is causing a lot of concern. They can see on satellites how it influences local weather patterns. Gardens reduce ambient heat.

Using electricity created by burning fossil fuels creates heat at the source and at the destination. Rooftop solar cells, on the other hand, would take energy (heat) from the surrounding area, store it, and then people would use it inside later. Net heat emission is approximately 0.

Maybe a combination of rooftop gardens and solar cells would be optimum?

I'm not a complete idiot -- some parts are missing.

EmptyKube's picture

Re:Interesting Article

There's another technology for producing electricity called thermophotovoltaic which takes heat and tranforms it to electricity the same way regular photovoltaics transform light into electricity. Imagin coating miles of blacktoped roadways with thermophotovoltaics, and collecting all that excess city/roadway heat into useable electricity. I wonder if a system could be devised to uses such collectors to transfer power to electric vehicles as they drove around?mmmm...

Re:Interesting Article


There are lots of places where those would be useful. How about putting thermophotovoltaics in a car engine? Maybe for a hybrid gas/electric vehicle?

Or how about in a coal fired power plant? The excess heat from burning coal could be used to create a little more electricity.

In fact, since the most common waste product of any form of energy creation is heat, one could theoretically use these anywhere.

A quick Google search turned up a few hits. It looks like there is much activity on them. I saw something on hybrid vehicles too. I couldn't find anything on their efficiency though... how "good" are they?

I'm not a complete idiot -- some parts are missing.

Re:Interesting Article

I read an article about thermophotovoltaic power a few years ago. From what I remember, the cells only work when exposed to certain frequencies of infared light, which was usually created by burning natural gas. They do not convert all heat energy to electricity. The article did not make it sound as if it was going to be a viable power source for everyone in the near future. Right now, apparently, it only has a few niche applications.

To err is human. I am not human.

Re:Interesting Article

Bummer. That explains why they call it thermo[i]photo[/i]voltaic.

Still, anything that gives off heat should give off at least some IR.

I'm not a complete idiot -- some parts are missing.