Clean Power

Published on August 16th, 2013 | by Nicholas Brown


New Plastic Solar Cell Design Promises Bright Future

August 16th, 2013 by  

With the world’s population is growing so quickly, how will we all be supplied with electricity sustainably? Reserves of all the major fossil fuels are dwindling more and more rapidly due to demand increases.

As these supplies diminish, they become impractically expensive for more and more people. Plus, there is global warming to deal with! Fortunately, solar panels don’t automatically become more expensive when electricity demand increases. When you buy your own solar panels, you lock in your electricity rate for the next 30 years or more!

An improvement in plastic solar cell design could help to make this easier for more people and applications. Researchers, including students and faculty members at Northwestern University, led by Tobin J. Marks have developed a new polymer (plastic) solar cell with a fill factor of 80%.

plastic solar cells

Nature Journal Article Figure 2: Device architecture and performance of inverted BHJ polymer solar cells. a, Inverted device architecture, ITO/ZnO/polymer:PC71BM/MoOx/Ag. b, Energy level diagrams for PTPD3T, PBTI3T and PC71BM. c, J–V characteristics of PTPD3T:PC71BM and PBTI3T:PC71BM BHJ inverted solar cells fabricated using chloroform (CF)…

“Our results indicate that the power-conversion efficiency achievable with polymer solar cells may be far beyond the current levels, heralding a bright future for this technology,” Marks said. “With our high fill factors, polymers with very good but not champion light absorption still are able to achieve very good efficiency.”

According to Northwestern University’s website:

The team showed that the exceptional fill factors arise from high levels of order in the mixture of polymer donor chains and buckyball acceptor components, the way these two components are distributed within the cell active layer, and a ‘face-on’ orientation of the polymer chains on the electrode surface.

The fill factor achieved is more than 10 percent greater than previously achieved by the polymer solar cell community, and, in the present study, although the polymer semiconductors have non-optimal light absorption characteristics, a near-record power-conversion efficiency as high as 8.7 percent is still obtained.

Apart from Tobin J. Marks, the other authors of the paper are Xugang Guo, Nanjia Zhou, Sylvia J. Lou, Jeremy Smith, Daniel B. Tice, Jonathan W. Hennek, Rocío Ponce Ortiz, Shuyou Li, Lin X. Chen, Robert P. H. Chang and Antonio Facchetti, of Northwestern; Juan T. López Navarrete, of the University of Malaga, Spain; and Joseph Strzalka, of Argonne National Laboratory.

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About the Author

writes on CleanTechnica, Gas2, Kleef&Co, and Green Building Elements. He has a keen interest in physics-intensive topics such as electricity generation, refrigeration and air conditioning technology, energy storage, and geography. His website is:

  • Doug

    I have no idea what the article is about. ???

    • Yeah, it’s something about a more efficient “fill factor” for some technical reason, which results in a bit more power. Not well explained, and perhaps not very significant. Good excuse to pick on several other implied assumptions in the article.

  • mds

    Mr. Brown is fundamentally and obviously correct that increasing energy use cannot be sustained by limited fossil fuel resources. The most immediate problem is the rest of the world (esp China and India) would like to live closer to the standard of living the western world has ..and this requires more energy. The continuing increase in human population is also a factor, right now and into the future.
    In fact, the on going increase in human population is and will continue to be the cause of most of our real problems. Life could be so much better for all if we could figure out how to fairly and justly control the numbers of humans on the plant. The energy problem is an easy one to solve. I don’t see how to solve the over-population problem.

    • Bob_Wallace

      “I don’t see how to solve the over-population problem.”

      How about this. We go down the list of countries with the highest birthrates and identify some where we could build some factories/shops which have high low-skilled labor needs. For example, garment factories.

      Go into those countries and set up factories and pump up the schools for the children of workers (and other is possible). If the culture permits then set up some birth control clinics where people could receive education and “necessary goodies”.

      We’re growing the world’s population at only 1%. It might take 10, 15, 20 years to have a big impact on that extra 1%, but if we got going we could plateau pop-growth out in a generation.

    • “the on going increase in human population is and will continue to be the cause of most of our real problems.” Wrong for several reasons.

      Population has peaked and stabilized several times in the past, and that certainly *could* happen again. Population even declines when there are more deaths than births (e.g. during the black plague). But each time, technology and health care improvements have allowed more people to live, and in particular, more children to survive childhood. While the birth rate is declining pretty much everywhere now, the death rate is declining a bit faster, so it appears people are having more children. But they are not.

      Also, as I pointed out before, the use of resources and pollution of the environment is not evenly divided among the population, and it turns out that a very small fraction is responsible for most of the use of resources, and most of the pollution and destruction of the environment. It is not about how many people there are but how a few people are causing most of the problems. And then a few people turn around and blame the rest of the population.

      In the energy sector, we are phasing out fossil fuels, moving toward more and more renewable energy. We are only at 25% now, but once we get to 100% renewable energy, we’ll find that there is still 1000s of times more energy available to us, so we will likely continue to grow. We will also need to move toward 100% recycling of all our resources, zero waste, and zero pollution, which is a harder goal, but certainly possible. We should be able to grow all our food with no additional land, building vertical farms instead. Once we get there, we will have achieved Zero Footprint, at which time it won’t matter how many people we add to the population.

      So population is not the problem. Unsustainable practices by a few people is the main problem. And blaming the population as a whole for the sins of a few is also a problem because it hides the real problem.

  • mds

    “With the world’s population is growing so quickly, how will we all be supplied with electricity sustainably? Reserves of all the major fossil fuels are dwindling more and more rapidly due to demand increases.”

    Instead of saying “rubbish”, what if we offer a possible correction to this:

    First of all, what has been happening with oil is that new supply is having a difficult time keeping up with new demand. This due to increasing demand from China and India and to dwindling supplies of easy to get at oil. This is why the price of oil, gasoline, and diesel are staying high.

    Second, coal will be next. If renewables are not used to generate more of the electricity India and China want to use, then coal will be. If this happens the worlds coal will be used up in a few short decades and we will cook ourselves that much faster. Even if you don’t believe in AGW the result of continued dependency on coal for electricity will be the source of next World War within the time-frame of this century if we don’t meet our energy needs differently. Wars are sparked by nonsense, but are driven by conflicts over resources. In WW2 the German’s and Japanese needed more territory and access to more resources, particularly oil.

    Third will be Natural Gas (NG). Yes we will run out rapidly if we attempt a long term replacement of oil use with NG.

    Human population will not “plateau”. Sorry, wishful thinking. When has this ever happened in the history of the world? Human population growth will slow, but will not stop growing until the four horsemen ride again: the white horse (an evil and charismatic leader, e.g. Hitler), the grey horse (inflation), the red horse (war), and the black horse (death from starvation, disease, war, and wild animals). [No the four horsemen are not “war, disease, starvation, and pestilence” that is a misconception from a painting by Luther. Think about it, disease and pestilence is redundant, doesn’t make sense.] Your scary piece of wisdom for the day. Use those condoms and tell your kids how to use them! …and any other form of birth-control that works!

    • Bob_Wallace

      You should take a look at what is happening to the world population. Look at how many countries have a >0% and a <0% population growth and where they are. Look at how many are actually losing population.

      Between 2005 and 2010 there were 204 countries with population growth. By 2012 that had fallen to 188.

      What seems to work best for population control is education and jobs for women. And easy access to birth control technology.

      China may do the world a large favor by moving some of its lowest skill manufacturing to some of the least developed countries. Garment factories and electronics assembly operations tend to hire a lot of women.

  • “With the world’s population is growing so quickly …” Rubbish.

    First, population growth is far less than the growth of consumption, and the population growth is decreasing pretty much everywhere, and is projected to plateau at just 30-50% growth in 50 years relative to today, while energy consumption is projected to double in 50 years.

    Second, the rate of population growth is lowest where current consumption is highest, and conversely, the highest population growth is in the areas of the world with the smallest footprint. The poorest 50% of the world is responsible for only 7% of the total footprint.

    Third, new construction of energy production can now be 100% renewable, so developing counties will be able to leapfrog us. It is true that the developing parts of the world will be increasing their energy consumption, though it is not because their population is growing. It is simply because they have so little now.

    • Bob_Wallace

      Good points.

      What we need is a) for EOS System’s zinc-air battery to prove itself and b) for them to produce a “small household” size version. Something that would go head to head with a standard lead acid battery. Make it possible for people to start with micro-solar and build a larger system a step at a time.

      Do that and fossil fuels would never gain a toehold in less developed areas.

  • JamesWimberley

    “Reserves of all the major fossil fuels are dwindling more and more rapidly due to demand increases.“ Rubbish. There is far more coal than humanity can afford to burn if we want a liveable climate. It doesn´t matter how cheap or expensive fossil fuels are, they have to go anyway.

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