Today's heavy silicon panels are effective, but they can also be expensive and unwieldy. Searching for alternatives, William Dichtel, assistant professor of chemistry and chemical biology, and Eric L. Spitler, a National Science Foundation American Competitiveness in Chemistry Postdoctoral Fellow at Cornell, employed a strategy that uses organic dye molecules assembled into a structure known as a covalent organic framework (COF). Organic materials have long been recognized as having potential to create thin, flexible and low-cost photovoltaic devices, but it has been proven difficult to organize their component molecules reliably into ordered structures likely to maximize device performance.
"We had to develop a completely new way of making the materials in general," Dichtel said. The strategy uses a simple acid catalyst and relatively stable molecules called protected catechols to assemble key organic molecules into a neatly ordered two-dimensional sheet. These sheets stack on top of one another to form a lattice that provides pathways for charge to move through the material.
The reaction is also reversible, allowing for errors in the process to be undone and corrected. "The whole system is constantly forming wrong structures alongside the correct one," Dichtel said, "but the correct structure is the most stable, so eventually, the more perfect structures end up dominating." The result is a structure with high surface area that maintains its precise and predictable molecular ordering over large areas.
The researchers used x-ray diffraction to confirm the material's molecular structure and surface area measurements to determine its porosity.
At the core of the framework are molecules called phthalocyanines, a class of common industrial dyes used in products from blue jeans to ink pens. Phthalocyanines are also closely related in structure to chlorophyll, the compound in plants that absorbs sunlight for photosynthesis. The compounds absorb almost the entire solar spectrum – a rare property for a single organic material.
"For most organic materials used for electronics, there's a combination of some design to get the materials to perform well enough, and there's a little bit of an element of luck," Dichtel said. "We're trying to remove as much of that element of luck as we can."
The structure by itself is not a solar cell yet, but it is a model that will significantly broaden the scope of materials that can be used in COFs, Dichtel said. "We also hope to take advantage of their structural precision to answer fundamental scientific questions about moving electrons through organic materials."
Once the framework is assembled, the pores between the molecular latticework could potentially be filled with another organic material to form a light, flexible, highly efficient and easy-to-manufacture solar cell. The next step is to begin testing ways of filling in the gaps with complementary molecules.
The article, "Lewis acid-catalysed formation of two-dimensional phthalocyanine covalent organic frameworks," appears in the online edition of the journal Nature Chemistry, June 20, 2010. The National Science Foundation provided funding for this research.
Blaine Friedlander | EurekAlert!
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy