Free Republic
Browse · Search
Topics · Post Article

Skip to comments.

Organic Crystal Allows Excitons to Travel Further, Produces More Efficient Plastic Solar Cells
Daily Tech ^ | October 11, 2010 10:56 AM | Tiffany Kaiser

Posted on 10/12/2010 10:33:05 AM PDT by Ernest_at_the_Beach

Rubrene crystal raises hope for the use of organic semiconductors and cheaper, more efficient solar cells

Rutgers University physicists have found new properties within a material that could lead to the production of less expensive and more efficient plastic solar cells.

Vitaly Podzorov, co-author of the study and assistant professor of physics at Rutgers University, along with his research team have discovered that organic semiconductors allow energy-carrying particles -- which are created by "packets" of light -- to journey a thousand times farther than researchers previously thought. 

"Organic semiconductors are promising for solar cells and other uses, such as video displays, because they can be fabricated in large plastic sheets," said Podzorov. "But their limited photovoltaic conversion efficiency has held them back. We expect our discovery to stimulate further development and progress.

Podzorov and his team came to these conclusions by observing excitons, which are particles that consist of an electron and an electron hole where a positive charge is attributed to the absence of an electron. Excitons form when semiconducting materials absorb photons, which are light particles.

The problem with organic semiconductors up until this point was that they were observed to travel less than 20 nanometers. This is an issue because electrons and the holes move to the two opposite sides when they "hit" a semiconductor junction or boundary. If these excitons only diffuse "tens of nanometers," the only ones that generate photo-voltage are those closest to the boundaries or junctions. 

"Now we lose 99 percent of sunlight," said Podzorov. 

But now, Podzorov and his team have observed that excitons can journey a thousand times farther than previously thought in rubrene, which is an extremely pure crystal organic semiconductor

"This is the first time we observed excitons migrating a few microns," said Podzorov. "Once the exciton diffusion distance becomes comparable to the light absorption length, you can collect most of the sunlight for energy conversion."

Excitons within the rubrene crystal acted like excitons in inorganic crystals, which means better opto-electronic properties, increased efficiency and lower costs. Podzorov and his team hope, with further development, that solar cells based on this technology can replace silicon solar cells.

In the midst of this research Podzorov also discovered a new way of measuring excitons based on optical spectroscopy. Excitons are hard to measure because they are not charged, so the Rutgers University research team created a new method called polarization resolved photocurrent spectroscopy, which "dissociates" excitons at the surface of the crystal and exposes large photocurrent. 

This study will be in an upcoming issue of Nature Materials, where Podzorov has submitted other relevant and recent research on organic semiconductors. 

TOPICS: Business/Economy; Science
KEYWORDS: allows; cells; crystal; efficient; energy; excitons; further; organic; plastic; produces; rubrene; solar; solarcells; stringtheory; travel

1 posted on 10/12/2010 10:33:13 AM PDT by Ernest_at_the_Beach
[ Post Reply | Private Reply | View Replies]

To: Ernest_at_the_Beach


2 posted on 10/12/2010 10:36:38 AM PDT by svcw (Just in case you ever wondered: As of May 2010, it costs ~ $0.0167 US Dollars to mint a penny.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: Ernest_at_the_Beach

but will they power a warp engine?

3 posted on 10/12/2010 10:39:08 AM PDT by GeronL ( <--- My Fiction/ Science Fiction Board)
[ Post Reply | Private Reply | To 1 | View Replies]

To: Ernest_at_the_Beach

bump for later

4 posted on 10/12/2010 10:50:31 AM PDT by Slyfox
[ Post Reply | Private Reply | To 1 | View Replies]

To: Ernest_at_the_Beach


Rubrene (5,6,11,12-tetraphenylnaphthacene) is a red colored polycyclic aromatic hydrocarbon. Rubrene is used as a sensitiser in chemoluminescence and as a yellow light source in lightsticks.

As an organic semiconductor, the major application of rubrene is in organic light-emitting diodes (OLEDs) and organic field-effect transistors, which are the core elements of flexible displays.

5 posted on 10/12/2010 10:53:52 AM PDT by epithermal
[ Post Reply | Private Reply | To 1 | View Replies]

To: epithermal
Google turns up a number of references....including this one:

Role of synthesis for oxygen defect incorporation in crystalline rubrene

And a picture:

Packing of rubrene molecules (Carbon atoms in the tertacene backbone are coloured yellow for clarity).

6 posted on 10/12/2010 11:00:26 AM PDT by Ernest_at_the_Beach ( Support Geert Wilders)
[ Post Reply | Private Reply | To 5 | View Replies]

To: GeronL

Are these the same as Dilithiam Crystals?

7 posted on 10/12/2010 11:06:52 AM PDT by SoldierDad (Proud Papa of two new Army Brats! Congrats to my Soldier son and his wife.)
[ Post Reply | Private Reply | To 3 | View Replies]

To: Ernest_at_the_Beach
I hope this is a true step forward toward finally realizing cost-effective solar power, but I am skeptical. We've heard similar claims for decades, yet solar cell efficiency has barely improved at all.

It would be great if we could reach the point where each home produces its own power, especially as a defense against potential terrorist attacks on the electrical grid, but so far the economics just aren't there. All of the larger solar power projects across the country that are being touted by liberals are just for show. None of them make sense economically.

8 posted on 10/12/2010 11:09:06 AM PDT by noiseman (The only thing necessary for the triumph of evil is for good men to do nothing.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: Ernest_at_the_Beach

Interesting article. I have never had organic chemistry, but have had more than my share of advanced mineralogy, which is basically the chemistry of silicates. This article brings back a lot of memories of the complexity of the subject.

9 posted on 10/12/2010 11:13:52 AM PDT by epithermal
[ Post Reply | Private Reply | To 6 | View Replies]

To: Ernest_at_the_Beach; epithermal

So if there is more conductivity with the oxygen defect does it’s presence lessen the initial capturing of photons by a more pure form of the rubrene?

10 posted on 10/12/2010 11:39:40 AM PDT by bigheadfred ("We built a tower of stone. With our flesh and bone. To see him fly ." (RIP RJD))
[ Post Reply | Private Reply | To 6 | View Replies]

To: SoldierDad
No, and do not ask again!

11 posted on 10/12/2010 11:47:35 AM PDT by Dahoser (Separation of church and state? No, we need separation of media and state.)
[ Post Reply | Private Reply | To 7 | View Replies]

To: Dahoser
Are these the same as Dilithiam Crystals?

Now whatcha gonna do?

12 posted on 10/12/2010 12:31:30 PM PDT by SoldierDad (Proud Papa of two new Army Brats! Congrats to my Soldier son and his wife.)
[ Post Reply | Private Reply | To 11 | View Replies]

To: AdmSmith; bvw; callisto; ckilmer; dandelion; ganeshpuri89; gobucks; KevinDavis; Las Vegas Dave; ...
Thanks Ernest_at_the_Beach.

· String Theory Ping List ·
Sorry we re open
· Join · Bookmark · Topics · Google ·
· View or Post in 'blog · post a topic · subscribe ·

13 posted on 10/14/2010 8:32:03 PM PDT by SunkenCiv (The 2nd Amendment follows right behind the 1st because some people are hard of hearing.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: noiseman
No matter what the efficiency, PVs need an energy input in the form of sunlight. There's this natural phenomenon called “night”, and the input drops to zero during that time. Factor in less-than-optimum daytime conditions (clouds, sun angle, etc.), you're probably talking about even lower capacity factors. Sure, when they're working and producing output, your fuel cost is essentially zero, but if you don't have the energy when you need it, you're probably not going to be too happy, low fuel cost or no.
14 posted on 10/14/2010 8:43:32 PM PDT by chimera
[ Post Reply | Private Reply | To 8 | View Replies]

To: chimera
I totally agree, that is why we need to develop a commercial space industry in order to develop cheap solar power in space where can effectively develop this and other solar smelting technologies to there fullest potential, the only problem is that we do not currently have a low cost to orbit, this will either require nuclear technology which the public is currently not going to support or an effective governmental program to create a “space interstate” system along the lines of what was developed after WWII, also not currently publicly supported. We can, in time, transfer much of our production to an environmentally safe and economically sound manufacturing process, but it will take changing public perceptions and biases, good luck with either.

Forgive the format of my post and any spelling or grammatical errors, first post I have done via my cell phone

15 posted on 10/14/2010 9:27:32 PM PDT by tricky_k_1972 (Putting on Tinfoil hat and heading for the bomb shelter.)
[ Post Reply | Private Reply | To 14 | View Replies]

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794 is powered by software copyright 2000-2008 John Robinson