Obtaining this information is a critical step in the development of a new class of solar cells, which promise significant savings in production costs compared to conventional silicon-based cells. The new analytical technique, published as the cover story in this week's issue of the Journal of Physical Chemistry B, was developed by a team led by Penn State University researcher John B. Asbury, assistant professor of chemistry.
Organic photovoltaic devices (OPV) have become important because they are much less expensive to produce than silicon-based solar cells. The material consists of a film made of two different types of chemicals: a polymer that releases an electron when it is struck by a photon of light and a large molecule that accepts the freed electrons, which is based on the soccer-ball-shaped "buckminsterfullerene" carbon molecules popularly known as "buckyballs." Because the electrical interactions needed to produce an electric current occur at the interfaces of the two components of this polymer blend, materials scientists need to understand the arrangement of molecules in the film. Asbury's new analytical technique provides a closer look at this arrangement than the techniques that traditionally have been used. Previous studies, using atomic-force microscopy, supply general information about the packing of the molecules, but they provide very limited information about the interfaces where the molecules actually come together. IR spectroscopy, on the other hand, provides a more detailed picture of the interface by tracing the exchange of electrons between two molecules of the film.
"The problems with OPVs today are that they are not efficient enough and they tend to stop working over time," says Asbury. In order to develop a useful electric current, the flow between the two components must be optimized. "To improve performance, we need to understand what happens at the molecular level when light is converted to electrons," Asbury explains.
When the film is exposed to light, each photon excites an electron in the polymer. If an interface between the polymer molecule and the functionalized buckminsterfullerene exists, a current can be produced. However, in the materials developed to date, many of the electrons appear to become sidetracked. Asbury exposes the film to light using ultrashort laser pulses, which causes photons of light to be converted to electrons across the entire surface at the same time. Two-dimensional IR spectroscopy is used to monitor the vibration of the molecules within the film. "The vibrations of the molecules are strongly affected by the presence or absence of electrons," says Asbury. "We use these vibrations as a probe to track the movement of electrons. By varying the structures of the materials, we expect to identify the side paths that reduce efficiency and ultimately to use that information to guide material design." The ultimate goal is a solar cell that is sufficiently inexpensive and efficient that it can be used on a rooftop to provide the electrical energy needed in a building.
In addition to Asbury, the Penn State research team includes graduate students Larry W. Barbour and Maureen Hegadorn. The work was funded by the Camille and Henry Dreyfus Foundation, the Petroleum Research Fund, and Penn State.
Barbara K. Kennedy | EurekAlert!
From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison
Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
23.02.2017 | Physics and Astronomy
23.02.2017 | Earth Sciences
23.02.2017 | Life Sciences