Escape route: Electrons created in a nanoparticle-based solar cell have to follow a circuitous path (red line) to reach an electrode. Many don't make it, lowering the efficiency of these cells. Researchers at Notre Dame have used carbon nanotubes to help the electrons reach the electrode, improving efficiency.
Prashant Kamat
Carbon nanotubes could help make nanoparticle-based solar cells more efficient and practical.
Researchers at University of Notre Dame, in Indiana, have demonstrated a way to significantly improve the efficiency of solar cells made using low-cost, readily available materials, including a chemical commonly used in paints.
The researchers added single-walled carbon nanotubes to a film made of titanium-dioxide nanoparticles, doubling the efficiency of converting ultraviolet light into electrons when compared with the performance of the nanoparticles alone. The solar cells could be used to make hydrogen for fuel cells directly from water or for producing electricity. Titanium oxide is a main ingredient in white paint.
The approach, developed by Notre Dame professor of chemistry and biochemistry Prashant Kamat and his colleagues, addresses one of the most significant limitations of solar cells based on nanoparticles. (See "Silicon and Sun.") Such cells are appealing because nanoparticles have a great potential for absorbing light and generating electrons. But so far, the efficiency of actual devices made of such nanoparticles has been considerably lower than that of conventional silicon solar cells. That's largely because it has proved difficult to harness the electrons that are generated to create a current.
Indeed, without the carbon nanotubes, electrons generated when light is absorbed by titanium-oxide particles have to jump from particle to particle to reach an electrode. Many never make it out to generate an electrical current. The carbon nanotubes "collect" the electrons and provide a more direct route to the electrode, improving the efficiency of the solar cells.
As they wrote online in the journal Nano Letters, the Notre Dame researchers form a mat of carbon nanotubes on an electrode. The nanotubes serve as a scaffold on which the titanium-oxide particles are deposited. "This is a very simple approach for bringing order into a disordered structure," Kamat says.
The new carbon-nanotube and nanoparticle system is not yet a practical solar cell. That's because titanium oxide only absorbs ultraviolet light; most of the visible spectrum of light is reflected rather than absorbed. But researchers have already demonstrated ways to modify the nanoparticles to absorb the visible spectrum. In one strategy, a one-molecule-thick layer of light-absorbing dye is applied to the titanium-dioxide nanoparticles. Another approach, which has been demonstrated experimentally by Kamat, is to coat the nanoparticles with quantum dots--tiny semiconductor crystals. Unlike conventional materials in which one photon generates just one electron, quantum dots have the potential to convert high-energy photons into multiple electrons.
Several other groups are exploring approaches to improve the collection of electrons within a cell, including forming titanium-oxide nanotubes or complex branching structures made of various semiconductors. But experts say that Kamat's work could be a significant step in creating cheaper, more-efficient solar cells. "This is very important work," says Gerald Meyer, professor of chemistry at Johns Hopkins University. "Using carbon nanotubes as a conduit for electrons from titanium oxide is a novel idea, and this is a beautiful proof-of-principle experiment."
Researchers find a new way to make cheap and flexible photovoltaic cells.
hers is the least expensive solar solution
I hope this research continues. There is a solar solution that consumers can take advantage of right now. I am a manager with a brand new company called CitizenRe. If you ever wanted to help the environment and get most of your energy from the sun and not from your dirty energy provider,this company will provide you a solar solution with NO UPFRONT COST! please investigate and continue discussion in this thread:
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Re: hers is the least expensive solar solution
Solarnow,
CitizenRe is a scam, they don't produce anything, they are not gonna deliver.
...And you know it!
More info e.g. :
www.renewableenergyaccess.com/rea/news/podcast?id=47452
grts
Bruno M.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Re: hers is the least expensive solar solution
The gasoline shortage in the 70's made me realize that the days of hydrocarbons were numbered.
I know zilch technicaly but I know disaster when I see it approaching. The expense bugaboo has been the excuse for looking everywhere but at solar to solve our energy problems. We, a country that could casually blow away 500 billion to protect our S&L's and is now dumping 750 billion into the Iraq garbage pit should not shy away from whatever it costs to go solar / hydrogen.
It is amazing that building poorly performing solar cells get such press. Just as in the case of Nanotubes in polymers (APL some years ago) there are real engneering challenges that must be overcome before this approaches usable numbers (such as balancing charge mobility, since the mobility of electrons in nanotubes and holes in TiO2 are decidely different can this be done?). And what about the natural tendancy of nanophase titania to act as a highly effecient photocatalyst? Is it reasonable to think that lifetimes can be extended beyond what we now know from graetzle configurations? The paper presented addresses none of these challenges or offers any reason to think that they can be overcome.
And yet, there are some significant performance increases being made in organic solar cells (two new papers out this past month). These never seem to make the press. Oh... But these dont use nanotubes so I guess they dont count.
i would like to know in what journal those two papers about organic solar cells are.
thanx
I also would like to know about these 2 articles on organic solar cells
Thanks
I like to know about the significant performance increases being made in organic solar cells two new papers out this past month.
Regards,
Raul
cheap solar energy.. a way into the future
It would be really nice if solutions like these were used by common folks to set up ad hoc electrical supplies for their domestic needs. If the government bolsters the concept by providing tax breaks, it would be even cheaper and people would definitely show some interest in migrating to the new technology.
Mahurshi Akilla
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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ta-knut
3 Comments
Problem wiht UV-light?
What's the problem with using UV-light instead of visible light? Isn't there enough UV-light around for this to be effective? At least when thinking about the future, considering that the ozon layer is getting thinner and thinner, letting more UV-light trough!
Reply
Colin
8 Comments
Re: Problem wiht UV-light?
It's not a problem, it's an opportunity. There are several other organic thin film solar cell projects that have not yet achieved high efficiency conversion of photons to electricity. If they can take advantage of single wall carbon nanotube mats AND add a layer of UV sensitive titanium dioxide, it's win-win. I sure hope somebody can do this or something like it.
Colin
Reply
desolation0
13 Comments
The Problem with UV-light...
is a question of bang for the buck. While there is alot of UV light coming to Earth, it is not as efficient to collect only the UV light. A less efficient collector at more wavelengths will almost always absorb more energy than a highly efficient collector dedicated to just a short range.
Reply
chresourceint
1 Comment
Re: Problem wiht UV-light?
i am sending an excutive summary of a 10000MW hybrid solar bio fuel and municiple waste initiative in india.
with regards
Pulak Chowdhury
Team Leader and Advisor
00-91-9213059375
Pulak Chowdhury
Team Leader and Advisor
Chowdhurys Solar & Renewable Research Initiative
111, Royal Residency, plot no 5, Sector9, Dwarka, and New Delhi, India 110075
e-mail: chresourceint@gmail.com,solarpowerproject@hotmail.com
00-91-11-9213059375
Executive Summary
Seasons greetings, it is a pleasure to introduce Chowdhurys Solar &
Renewable Research Initiative, world first ever Integrated 10000Hybrid Solar+ Bio Fuel ( Bio Fuel)+ Municipal waste Initiative in State of Karnataka (Ban galore). Out of which 2Gwatt we will feed to the state grid and remaining solar panels will be exported to Germany, US,Australia, Europe, Gulf and Africa. Following are the Brief
1. The 10MW pilot project will cost $220 mn will run from 2008-2010 given the year wise.( Down stream refinery cost break up will be given later presently we are working out on feasibility report
2. We are planting Energy crop Jatropa and Karanja in over 11mn hectares fallow and wasteland where we have taken conservative harvest yield time in 36 months but in Zimbabwe the Jatropa seed taken from
India gave Harvest in 18 months.
3. With 5% blending India will need 2mmtons of Bio Fuel (Bio Diesel), and with 10% blending we need 4mmtons of Bio Fuel, from our Initiative we can export 7-9 mm tons of Bio Diesel.
4. We have planned for 4 down stream Refinery to cover all parts of India, which has 100-150 mn hectares fallow and wasteland we have scanned entire state of Karnataka which has 2mn hectares waste and Fallow land in other states are also the base line study is on Since
Jatropa will give Harvest for next 50 yrs.
5. We are also developing Home solutions for Condominiums and row houses.
6. Carbon credit will be the spin off benefit
7.Eveluserver of Luxembourg is doing the worldwide patent filling for our Hybrid Solar +Bio Fuel +Municipal waste on Nano Research
We have gone through the Details of BTL Technology initiative and
some points will be relevant for kind perusal of the project.
8. From 11mn hectares land $5bn Bio diesel every year can be made for 50 yrs. From 4th yrs, onward.The breaking News coming from Zimwabe where the seedlings taken from India for Jatropa and Karanaja the harvest has come in 18 months
9 Nano research Initiative will have field trial for developing duel fuel engines to run on Bio Diesel and Gasoline both.
10.Heads of to German Innovations I have made a comprehensive strategy to have parallel cash flow since my research Initiative will need good chunk of liquidity so to have a balancing act by off setting cost with
Hybridizing the system with wind ect, in Night time when no sunlight the wind is there.
11. Complete production chain from Planting and cultivation of good quality Jatropa seed.
12 Four Standardized Green field refineries will come in 4 corners of India to collect the Jatropa seed and Transesterification, out of which three will be close by to existing refineries and 4th own will be a modern one with Latest technology, evaluating the 5 technology mentioned for Bio-diesel production.
13. Good Infrastructure is available in four places identified by us.Nano research Initiative will supplement the larger scale BTL plant on can be examined by Evaluating, existing proven technology and pilot
and demonstration project to convert additional 10% (in access of 50%)that will give a wind fall.
Attaching here a series of presentation the Feed In Tariff Introduce in India recently with Rs.12 per kwh( 1$=Rs.40 only), The renewable space in Indian is witnessing 140%CARG, 30 % pre tax profit,10% tax Holidays as infrastructure project. Wich cheap labor and skilled
Scientist and researcher this is going to be a Project of Future in
192 countries.
Way forward
Phase I
10 MW Solar Power System (Only Solar) In State of Uttarakahand,Technical and Financial Bid already submitted $80mnIncluding Balance
of system Battery bank to feed in to grid
10000MW in state of Karnataka purely Solar out of which 2000MW will be
state Grid and rest 8000 MW will be exported to Germany, rest of
Europe US, Australia , Gulf, Africa .
Plantation of Jatropa and Karanaja in 11mn hectares waste and fallow
land already scanned 2mn Fallow and wasteland in state of Karnataka
and will expand in other states.
8,00,000 Tons per annum Bio Diesel refinery at Mangalore
5060 MW of waste to power 10.6mw each in 500 municipal corporation
country wide were I have municipal waste 800 tons per day
Phase II of this starting from 10 MW pilot project to scale up the
size to 100MW, 1000MW, 10000MW complete turnkey fabrication assembly
line
Satge II
Expanding the base to 23 more states in India from 2008-2017 where in
Totality 200000mw solar power can be harnessed
Expanding the Jatropa and Karnaja in additional 100 mn to 150 mn
hecres waste and fallow land country wide
Have three more Bio Diesel refinery one at Calcutta, One at Jabalpur
and One at Sindhudurg ( Maharastra ) to connect entire supply chain to
offset the High transesterification plant, my eye is also on cotton
seed oil and other non edible oils since Jatropa does not come Under
the Carbon Credit norms I can have Hybrid of 30%-70% ratio of Jatroap
and Karanaja the problem with Karanaja they are Plants of 50 ft and
will block the sun shine where Jatropa man 3 to 7 ft I can easily have
Mounting Solar panels
My worldwide patent on Nano technology will be out and I will
Implement this integrated project in 192 countries worldwide.
I am applying my mind how to calibrate the entire carbon credit
Component in entire renewable initiative. Kindly acknowledge my mail.
Pulak Chowdhury
Team Leader and Advisor
Chowdhurys Solar & Renewable Research Initiative
111, Royal Residency, plot no 5, Sector9, Dwarka, and New Delhi, India
110075 e-mail: chresourceint@gmail.com,solarpowerproject@hotmail.com
Cel:00-91-9213059375
Reply