October 13, 2005
UCLA Team Cuts Photovoltaics Cost With Plastics

A UCLA team may have found a path to make photovoltaics cost competitive.

In research published today in Nature Materials magazine, UCLA engineering professor Yang Yang, postdoctoral researcher Gang Li and graduate student Vishal Shrotriya showcase their work on an innovative new plastic (or polymer) solar cell they hope eventually can be produced at a mere 10 percent to 20 percent of the current cost of traditional cells, making the technology more widely available.

"Solar energy is a clean alternative energy source. It's clear, given the current energy crisis, that we need to embrace new sources of renewable energy that are good for our planet. I believe very strongly in using technology to provide affordable options that all consumers can put into practice," Yang said.

The use of purified silicon currently prevents photovoltaics from reaching cost competitiveness. Another approach being pursued is the development of plants for making less purified silicon. But the plastics approach bypasses the problem altogether.

The price for quality traditional solar modules typically is around three to four times more expensive than fossil fuel. While prices have dropped since the early 1980s, the solar module itself still represents nearly half of the total installed cost of a traditional solar energy system.

Currently, nearly 90 percent of solar cells in the world are made from a refined, highly purified form of silicon -- the same material used in manufacturing integrated circuits and computer chips. High demand from the computer industry has sharply reduced the availability of quality silicon, resulting in prohibitively high costs that rule out solar energy as an option for the average consumer.

Made of a single layer of plastic sandwiched between two conductive electrodes, UCLA's solar cell is easy to mass-produce and costs much less to make -- roughly one-third of the cost of traditional silicon solar technology. The polymers used in its construction are commercially available in such large quantities that Yang hopes cost-conscious consumers worldwide will quickly adopt the technology.

Independent tests on the UCLA solar cell already have received high marks. The nation's only authoritative certification organization for solar technology, the National Renewable Energy Laboratory (NREL), located in Golden, Colo., has helped the UCLA team ensure the accuracy of their efficiency numbers. The efficiency of the cell is the percentage of energy the solar cell gathers from the total amount of energy, or sunshine, that actually hits it.

The conversion efficiency they have achieved is not yet high enough. But they think they can achieve a 3 or 4 times increase in conversion efficiency to make it competitive.

According to Yang, the 4.4 percent efficiency achieved by UCLA is the highest number yet published for plastic solar cells.

"As in any research, achieving precise efficiency benchmarks is a critical step," Yang said. "Particularly in this kind of research, where reported efficiency numbers can vary so widely, we're grateful to the NREL for assisting us in confirming the accuracy of our work."

Given the strides the team already has made with the technology, Yang calculates he will be able to double the efficiency percentage in a very short period of time. The target for polymer solar cell performance is ultimately about 15 percent to 20 percent efficiency, with a 1520 year lifespan. Large-sized silicon modules with the same lifespan typically have a 14 percent to 18 percent efficiency rating.

Plastic decays in sunlight. So I'm not surprised by the projected 15 to 20 year lifespan. Other approaches as replacements for silicon could potentially last longer.

This development is not yet ready for market.

The plastic solar cell is still a few years away from being available to consumers, but the UCLA team is working diligently to get it to market.

"We hope that ultimately solar energy can be extensively used in the commercial sector as well as the private sector. Imagine solar cells installed in cars to absorb solar energy to replace the traditional use of diesel and gas. People will vie to park their cars on the top level of parking garages so their cars can be charged under sunlight. Using the same principle, cell phones can also be charged by solar energy," Yang said. "There are such a wide variety of applications."

Photovoltaics will become cost competitive some day. But it is very hard to guess when. The fact that talented groups of researchers (including some start-ups with funding from major venture capitalists) are working on approaches that avoid the high cost of silicon crystals makes me optimistic that a breakthrough will come within 10 years. We also still face the battery problem for how to store it for night use and also for transportation.

Share |      Randall Parker, 2005 October 13 08:18 AM  Energy Solar

Dan said at October 13, 2005 8:28 AM:

If the cost is low enough, the shorter life of the plastic substrate should not be problem. After 15 years, the new stuff available will be **way** more efficient. Given how our personal demand grows over time, that newer, more efficient set of cells will almost certainly be necessary. And nighttime isn't a problem in developed countries, because the delivery systems from conventional electrical generation sources will still be there. We just won't be drawing on it as heavily.

James Bowery said at October 13, 2005 10:18 AM:

The 4% efficiency isn't necessarily a record for polymer cells.

A prior advance in polymer solar cells:


had efficiency that dramatically varied with light intensity:

"Dr Paul Alivastos, of Berkeley's chemistry department, said that with the introduction of nanorods made from cadmium selenide (CdSe) with lengths varying from 7 to 60nm, a polymer cell achieved a solar conversion efficiency of 6.9% in a low light environment and 1.7% in normal solar conditions."

Ivan Kirigin said at October 13, 2005 10:51 AM:

Concerning storage for night-time...

How plausible is world-wide transfer of day-light energy?

Can you have generation units across the globe with power transfer from the brighter areas to the darker and from those under night to those in daylight?

I suppose this needn't be over ground, if the power is from cheap solar stations in space, with directed energy transfer between satellites and to the ground. This assumes, of course, something akin to a space elevator to make to-orbit transportation much cheaper.

Maybe this is just a habit of people being poor at predicting what will occur in 10-20, but it seems like plenty of things will change in that time frame, regardless of a "singularity":
A transition to solar, and the greater individual independence provided
Cheaper space access
Automated transportation (at the very least)

I could go on, but who needs a 3 paragraph futurist...

Travis Garrett said at October 13, 2005 11:14 AM:

We also still face the battery problem for how to store it for night use and also for transportation.

I think plug-in hybrids make a lot of sense in this regard. If the batteries in the car are good for 30-40 miles, i.e. most of the driving you'd do in an average day, then you could cut gasoline usage down by 90%. But you still have the long range given by the internal combustion engine if you want to drive to the beach on the weekend. Of course, you'll be gone during much of the day so the solar cells on your roof won't be charging your car then, but they could be spinning up a set of flywheels buried out in your backyard, which will then charge up your car when you plug it in at night. Plus, we can gradually move over to this system over time, eventually phasing out the gasoline engine as electrical storage methods improve, and it also works great in conjunction with building a bunch of new nuclear reactors (preferably breeders).

S. Cormack said at October 13, 2005 12:39 PM:


Back in July you posted this link: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2005/07/11/BUG7IDL1AF1.DTL

It seems that Nanosolar and others are well on their ways to fielding plastic photovoltaics.

Nick said at October 13, 2005 12:59 PM:

"We also still face the battery problem for how to store it for night use and also for transportation."

Does anyone have any recent info on the Toshiba battery? If the claims are accurate, it seems like a pretty important development (pretty much the battery breakthrough we've been waiting for, for 20 years), but I haven't seen anything since the press release around April..

Nick said at October 13, 2005 1:00 PM:

"We also still face the battery problem for how to store it for night use and also for transportation."

Does anyone have any recent info on the Toshiba battery? If the claims are accurate, it seems like a pretty important development (pretty much the battery breakthrough we've been waiting for, for 20 years), but I haven't seen anything since the press release around April..

AA2 said at October 13, 2005 2:30 PM:

Travis - That is what I think we will see is a move towards hybrid cars, then over time the battery will increase its ability to store energy per kilogram. And ultimately the gasoline engine will be phased out allowing an even larger weight battery.

Plug in hybrids are the early harbingers of the future to me. With increasing battery density like the lithium sulfur, and cheaper.. and much faster charging there is no argument for not going to an all electric.

Power from the grid is something like 3 cents a gallon in gasoline terms. And with electric cars you can have much less weight dedicated to an engine.. then of course with no moving parts and many fewer parts, cars will need little to no maintenance. Which is a large factor for commercial use especially.

Also when you put the electric motors in the wheels, you get performance boosts, handling boosts, smoother acceleration etc..

People are still talking hydrogen, but I think its obvious that isn't the way things are headed.

AA2 said at October 13, 2005 2:34 PM:

As for solar I think its a kewl idea and may have some good applications, but I think people are fighting against a powerful historical trend. And that is rising energy density from the fuel source. From wood, to coal, to oil/gas, to nuclear fission. Each step we see higher densities from the fuel. Solar you are limited by the amount of solar energy hitting each square meter.

Still it seems to be getting close to where companies like Walmart could put solar panels on the roof, and get cheaper electricity costs then from the grid.

gmoke said at October 13, 2005 2:47 PM:

Don't hold your breath for cheap PVs, plastic or otherwise, to enter the market. Start using solar PV where you can now and avoid the rush as well as the increasing fuel costs as we totter to peak oil and on down the other side of the bell curve.

Find Solar (http://www.ebike.net/solar/) has a quick solar calculator and links to local sources. You can plug in your state and county and estimate how much a solar installation (hot water, heating/cooling, electricity) will cost and what programs are available to offset some of those costs. My test shows some information to be out of date but it is a good place to start.

http://www.off-grid.net/index.php?p=487#more-487 documents a $600 solar system you can use for a modicum of emergency or day to day electricity

Ross Nizlek (ross.nizlek@uvm.edu), a student at UVM, has installed a 20 watt PV system on his dorm room. It powers all his personal electronics. He has documented the process at http://www.uvm.edu/~rnizlek/

Hugh Angell said at October 13, 2005 5:30 PM:

I'm not troubled by a 15 or 20 year lifespan for 'plastic' PV material. That is not far
from conventional roofing anyway. If it is lightweight it may even make up for its 'lower'
lifespan by the reduced cost of construction to say nothing of its energy production.

A lot of people would like a "Spanish" tile, slate or copper roofs because they look good
and last a long time. Alas, the cost of the material plus the need for stronger
trusses has made such construction prohibitive other than for top of the line homes.

A recent report suggested that if every roof in America were made of PV material the
output would exceed by two or three times the total electrical generation currently
produced in the US. Sorry I don't have the URL. It might even have been somewhat
optimistic. Needless to say we don't have to get there overnight nor include every
warehouse or shopping center as part of the figures to see that it is a goal worth
getting to.

Currently, in the real world, the number of people installing natural gas powered
electrical generators for their homes is remarkable. The recent rash of hurricanes
is an impetus. I dare say that, if, people were presented with a practical roofing
material and a couple of lead acid batteries that would keep their lights and
refrigerator running for a few days, the demand would be equally strong. We aren't
talking about having to sell only to survivalists and hermits. People will really
spend a few thousand dollars extra for a roof that can do it. I know, I have to
upgrade my consumers gas service to accomodate their generators. Whether my gas lines
will be able to accomodate that surge in demand, if the outage is widespread, is not
fully known. What I could tell such people is that, after the hurricane passes the
sun will shine and if they have 48 hours of battery capacity their 'roof' will provide
for their lights and refrigerator even if my gas lines are ruptured or lose pressure.

Sumyung Guy said at October 14, 2005 2:27 PM:

That nanosolar thing is very interesting, I wonder if any of you folks have heard anything else about them? Any news on just how well their product is working out?

PacRim Jim said at October 14, 2005 8:00 PM:

Are there any Americans doing research at American universities? Just asking.

Sione Vatu said at October 15, 2005 1:37 PM:

Quoting: "Also when you put the electric motors in the wheels, you get performance boosts, handling boosts, smoother acceleration etc.."

Surely not! By putting the motors in the wheels you have just increased the unpsrung mass of the car. Increasing the unsprung mass reduces mechanical grip and roadholding. It also wrecks the ride quality and increases tyre wear.

And how is putting the motor in the wheel going to give "smoother acceleration"?

Exposing an electric motor to the environment in the road wheel is not ideal. It's a bad place down there. Vibration levels are high, bearing loads are high and inertia effects are major. Not good for the motor at all.

The motors should be sprung mass. That means isolated from the wheels and above the springs.


Sione Vatu said at October 15, 2005 1:39 PM:

How much energy do the new cells take to manufacture?

What is the plastic feedstock and where does it come from?


Jacqui said at October 17, 2005 6:46 PM:

Sione, those are some good questions that deserve answers.

Hugh, I did find a study about how much land PV would need to provide the US with enough power. The article estimated 10 million acres, which is about 7% of the land taken by developed areas. Looking at Google satellite images, it looks possible to get this area from roofs. If it weren't enough, however, these cells can be installed as awnings and other building add-ons.

jimcrack said at October 18, 2005 6:22 PM:

I have the solution for nightime activity with solar cells! Turn on a light while you work with a PV appliance!

I'm not kidding. Virtually all PV appliances, such as radios, have demand for "high grade" electricity. You would not use a solar cell to run a lightbulb or boil water, because it is more efficient to let the sun shine. But these are irrelevant considerations in running a device that can only use electricity, or uses it with absolute efficiency (think of switches: you get the energy you want second by second, not easy to do with a fireplace). It happens that the convenience of portable power congrues with accessing it at night.

If the money California and other localities spent to subsidize photovoltaic farms had been spent to simply put small cells on millions of consumer appliances, mostly PC's, cell phones and the like, you would get something like the low expense, in power, that was already achieved in manufacturing the devices in the last 40 years.

This does not appeal to wonks who think in terms of how much intense sunlight we can soak up in an hour (a room light is not very intense, but a PV unit doesn't exactly drain light out of room), but it appeals to why we like electricity in the first place, which is to make life convenient. This is why we need cheapPVs that will work well in a darkened room.

Ken said at October 18, 2005 8:50 PM:

I believe PV will end up being everywhere. Techniques that can mass produce materials with customised structures with molecular precision are beginning to emnerge and that can only help make solar cells better and (hopefully) cheaper. I think the steps to get from what we have now (multiple alternate methods of producing PV and more emerging) to low cost high output PV production are far less formidable and therefore readily achivable than most of the alternatives. I find it odd that there are people who can see space based solar energy systems with all the high tech infrastructure that it entails as achievable but better batteries and cheap production methods for PV aren't. I'd have to say the same for Fusion. Whilst I wouldn't like to see the funding of research like ITER cut off, I truly believe we'd get more gigaWatts per megaDollar by matching that kind of funding to something that has more chance of paying off sooner, that can be deployed as quickly and easily in the developing world as the developed - and not have serious security implications that seem inevitable with massive worldwide expansion of nuclear fission. I'm all for Prof Smalley's Manhattan style project to develop enegy techonologies that will see the world well prepared for the future.

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