Engineering news
Researchers at Karlsruhe Institute of Technology (KIT), Germany, have developed a metal-organic material suited for photovoltaics.
For the first time, they were able to create a functioning organic solar cell consisting of a single component produced on the basis of metal-organic framework compounds (MOFs).
Thanks to their mechanical properties, MOF thin films of a few hundred nanometers in thickness can be used for flexible solar cells or for the coating of clothing material or deformable components.
Professor Christof Wöll, director of KIT Institute of Functional Interfaces (IFG), said: “While the demand for technical systems converting sunlight into electricity is increasing, organic materials represent a highly interesting alternative to silicon that has to be processed at high costs before it can be used for the photoactive layer of a solar cell.”
MOFs consist of two basic elements, metal node points and organic molecules, which are assembled to form microporous, crystalline materials. For about a decade, MOFs have been of considerable interest to researchers because their properties can be adjusted by varying the components. So far, more than 20,000 different MOF types have been developed and used mostly for the storage or separation of gases.
The team of scientists, under the direction of KIT, has now produced MOFs based on porphyrines. These porphyrine-based MOFs have a high efficiency in producing charge carriers. Examples of this can be found in nature, for example in hemoglobin and chlorophyll, where these organic dyes convert light into chemical energy.
A metal-organic solar cell produced on the basis of this novel porphyrine-MOF is now being proposed by the researchers at KIT. Wöll said that to increase photovoltaic capacity of a material you may “just need a single organic molecule in the solar cell.”
The researchers expect that the photovoltaic capacity of a material may be increased considerably” in the future by filling the pores in the crystalline lattice structure with molecules that can release and take up electric charges.
This process has been developed at KIT, with the crystalline frameworks being grown in layers on a transparent, conductive carrier surface to form a homogeneous thin film, called SURMOFs.
Wöll said: “The SURMOF process is suited in principle for a continuous manufacturing process and also allows for the coating of larger plastic carrier surfaces.”