Organic 2-D films could lead to better solar cells

Apr 12, 2011 By Lauren Gold
Organic 2-D films could lead to better solar cells
Molecular building blocks assemble on graphene to provide oriented and ordered covalent organic frameworks. (Fernando Uribe-Romo)

(PhysOrg.com) -- Solar cells made from organic materials are inexpensive, lightweight and flexible, but their performance lags behind cells that contain silicon or other inorganic materials. Cornell chemist William Dichtel and colleagues have found a way to synthesize ordered organic films that could be a major step toward solving this problem.

It's the first time researchers have been able to coax materials known as covalent organic frameworks (COFs) out of their common powdered form into flat sheets of precisely ordered molecules on a conductive surface. That clears a major hurdle toward using COFs to replace the more expensive, less versatile materials used in and other electronics today.

The research appears in the April 8 issue of Science.

COFs have a variety of properties that are not found in traditional organic polymers, including excellent , high surface area and permanent . But while researchers have identified them as intriguing candidates for such devices, they have been hamstrung by the fact that the materials normally exist only as insoluble powders.

Dichtel, assistant professor of chemistry and chemical biology, and colleagues developed a simple process for growing thin (25-400 nanometers thick) films of COFs on a surface of graphene, a single-atom-thick sheet of carbon. They used at the Cornell High Energy Synchrotron Source (CHESS) to determine the materials' structure and orientation. The COFs grow as continuous films of well ordered, stacked layers on the graphene surfaces.

Unlike the powder form, the films grown on transparent surfaces can be probed using modern optical measurements. Researchers can also vary the properties of the frameworks by altering the structure of their components.

"These materials are so versatile -- we can tune the properties rationally, rather than relying on molecules to pack into films unpredictably," Dichtel said.

To demonstrate, the researchers created three variations of the frameworks. Of the three, one shows particular promise for solar cells -- it uses molecules called phthalocyanines, which are commonly found in industrial dyes used in products from blue jeans to ink pens.

Phthalocyanines, which are related to chlorophyll, absorb light over most of the solar spectrum -- a rare property for a single .

"Obtaining these materials as films on electrode materials is a major step toward studying and using them in devices," Dichtel said. "This method represents a general way to assemble molecules on surfaces predictably. This work opens the door to take these materials in many other directions."

Explore further: Graphene reinvents the future

Related Stories

Atom-thick sheets unlock future technologies

Feb 03, 2011

(PhysOrg.com) -- A new way of splitting layered materials, similar to graphite, into sheets of material just one atom thick could lead to revolutionary new electronic and energy storage technologies.

Graphene electrodes for organic solar cells

Jan 06, 2011

A promising approach for making solar cells that are inexpensive, lightweight and flexible is to use organic (that is, carbon-containing) compounds instead of expensive, highly purified silicon. But one stubborn ...

Expanding the degrees of surface freezing

Mar 31, 2011

(PhysOrg.com) -- As part of the quest to form perfectly smooth single-molecule layers of materials for advanced energy, electronic, and medical devices, researchers at the U.S. Department of Energy's Brookhaven ...

Recommended for you

Graphene reinvents the future

20 hours ago

For many scientists, the discovery of one-atom-thick sheets of graphene is hugely significant, something with the potential to affect just about every aspect of human activity and endeavour.

Catalytic gold nanoclusters promise rich chemical yields

Aug 25, 2014

(Phys.org) —Old thinking was that gold, while good for jewelry, was not of much use for chemists because it is relatively nonreactive. That changed a decade ago when scientists hit a rich vein of discoveries ...

Copper shines as flexible conductor

Aug 22, 2014

Bend them, stretch them, twist them, fold them: modern materials that are light, flexible and highly conductive have extraordinary technological potential, whether as artificial skin or electronic paper.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Quantum_Conundrum
4 / 5 (1) Apr 12, 2011
*sigh*

Another "could lead to better solar cells" article.

Hell, if they all teamed up, they should be able to get at least 90% efficiency by now, because EVERYONE seems to have an improvement.