Featured Research

from universities, journals, and other organizations

Physicists explore the key energy transport process underlying solar energy harvesting

Date:
August 13, 2011
Source:
Lehigh University
Summary:
Physicists have developed an imaging technique that makes it possible to directly observe light-emitting excitons as they diffuse in rubrene, a new material being explored for its extraordinary electronic properties.

Top: Crystal facets and locations with exciton diffusion experimentation. A: Micrometer thin crystal on bc facet, with different orientation. PL pattern shows exciton diffusion effect in the thin crystal and below. B: Clean bc facet. C: Crystal facet where b axis is not parallel to the surface, producing asymmetric PL pattern.
Credit: Ivan Biaggio, Lehigh University

Two Lehigh physicists have developed an imaging technique that makes it possible to directly observe light-emitting excitons as they diffuse in a new material that is being explored for its extraordinary electronic properties. Called rubrene, it is one of a new generation of single-crystal organic semiconductors.

Related Articles


Excitons, which are created by light, play a central role in the harvesting of solar energy using plastic solar cells. The achievement by Ivan Biaggio, professor of physics, and Pavel Irkhin, a Ph.D. candidate, represents the first time that an advanced imaging technique has been used to witness the long-range diffusion of energy-carrying excitons in an organic crystal.

One way to understand the mechanics of excitons, says Biaggio, is to pour a cup of milk on the floor. The milk spreads out in all directions from the point of impact. How far it goes depends on the type of surface on which it lands. Now imagine that the milk has been replaced with particle-like bundles of energy and the floor with an ordered arrangement of organic molecules.

Biaggio's group used a focused laser beam to create the particles -- the excitons -- in a crystal made of organic molecules. They tracked the movements of the excitons over distances smaller than the size of a human hair by directly taking pictures of the light that they emit. Unlike the spilled milk, the excitons spread only in a direction corresponding to a particular arrangement of molecules.

Hope for overcoming a solar bottleneck

An understanding of exciton diffusion is critical for plastic solar cell technology, in which the absorption of light creates excitons instead of directly inducing a current, as it does in the most commonly used silicon systems.

After they are created in plastic solar cells, excitons diffuse toward specially designed interfaces where they drive electrons into an external circuit, creating the flow of electrons we know as electric current. This diffusion process is one of the technical challenges limiting the efficiency of plastic solar cells.

"This is the first time that excitons have been directly viewed in a molecular material at room temperature," said Biaggio. "We believe the technique we have demonstrated will be exploited by other researchers to develop a better understanding of exciton diffusion and the bottleneck it forms in plastic solar cells."

When will we have cheap and efficient plastic solar cells? It is the goal of researchers around the world to improve exciton diffusion lengths until they become as large as the light absorption -- that's the point when sunlight is most efficiently collected and converted into energy.

An article by Irkhin and Biaggio was published in the journal Physical Review Letters.

The work was supported by a Faculty Innovation Grant from Lehigh, which provides resources to develop novel ideas and demonstrate new approaches to important research questions.

Thanks to the direct imaging of the diffusing excitons, Irkhin and Biaggio were able to obtain precise measurement of their diffusion length. This length was found to be very large in a particular direction, reaching a value several hundreds of times larger than in the plastic solar cells that are presently used. This is the first time that excitons have been directly viewed in a molecular material at room temperature, and it is believed that the widespread adoption of the technique developed by Irkhin and Biaggio will lead to significant progress in the field.

"It is important that physicists explore the most fundamental phenomena underlying the mechanisms that enable solar energy harvesting with cheap organic materials," said Biaggio. "Organics have lots of unexplored potential and the very efficient exciton diffusion that we have observed in rubrene may build the basis for new ideas and technologies towards the development of ever more efficient and plastic solar cells."


Story Source:

The above story is based on materials provided by Lehigh University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Pavel Irkhin, Ivan Biaggio. Direct Imaging of Anisotropic Exciton Diffusion and Triplet Diffusion Length in Rubrene Single Crystals. Physical Review Letters, 2011; 107 (1) DOI: 10.1103/PhysRevLett.107.017402

Cite This Page:

Lehigh University. "Physicists explore the key energy transport process underlying solar energy harvesting." ScienceDaily. ScienceDaily, 13 August 2011. <www.sciencedaily.com/releases/2011/08/110812120914.htm>.
Lehigh University. (2011, August 13). Physicists explore the key energy transport process underlying solar energy harvesting. ScienceDaily. Retrieved December 18, 2014 from www.sciencedaily.com/releases/2011/08/110812120914.htm
Lehigh University. "Physicists explore the key energy transport process underlying solar energy harvesting." ScienceDaily. www.sciencedaily.com/releases/2011/08/110812120914.htm (accessed December 18, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Thursday, December 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
3D Printed Cookies Just in Time for Christmas

3D Printed Cookies Just in Time for Christmas

Reuters - Innovations Video Online (Dec. 18, 2014) A tech company in Spain have combined technology with cuisine to develop the 'Foodini', a 3D printer designed to print the perfect cookie for Santa. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Ford Expands Air Bag Recall Nationwide

Ford Expands Air Bag Recall Nationwide

Newsy (Dec. 18, 2014) The automaker added 447,000 vehicles to its recall list, bringing the total to more than 502,000. Video provided by Newsy
Powered by NewsLook.com
How Sony Hopes To Make Any Glasses 'Smart'

How Sony Hopes To Make Any Glasses 'Smart'

Newsy (Dec. 17, 2014) Sony's glasses module attaches to the temples of various eye- and sunglasses to add a display and wireless connectivity. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins