Watching scientists as they come up with new, amazing solutions for the world’s many needs in areas such as technology and energy is fascinating. Now researchers at the Karlsruhe Institute of Technology have found a way to use so called MOF-porphyrines in solar panels, possibly completely outmaneuvering silicon as a component.
Professor Christof Wöll, Director of KIT Institute of Functional Interfaces, speaks with great enthusiam about their new discovery: “We have opened the door to a new room. This new application of metal-organic framework compounds is the beginning only. The end of this development line is far from being reached.”
MOFs, or metal-organic frameworks, are composed of two elements: metal node points and organic molecules. These two parts are assembled together, forming crystalline, microporous materials.
The MOFs have been found very interesting in the scientific community for ten years now, thanks to the fact that those two components can be varied, thereby adjusting the functionality of the MOF. To be more precise, over 20,000 MOF types so far have been developed, and they are mainly used for storing or separating gases.
The study was published in the journal Angewandte Chemie International Edition, and the KIT scientist team were the ones to finally find a MOF based on porphyries. Such porphyrine-MOFs have a high efficiency in how they produce charge carriers with a high mobility of the carriers achieved. The photophysical properties of the newly found molecule are interesting, as they also indicate how the solar cells in the test function so well thanks to the formation of indirect band gaps. This is something that is highly important in photovoltaics.
Porphyrines, on their side, are universal molecules in nature, used in hemoglobin and chlorophyll to name a few, where they convert light into chemical energy.
“The clou is that we just need a single organic molecule in the solar cell. The researchers expect that the photovoltaic capacity of the material may be increased considerably in the future by filling in the pores of the crystalline lattice structure with molecules that can release and take up electric charges,” Wöll continues.
To make this whole piece of scientific magic work in real life, KIT has developed a process where the crystalline framework grows in layers on a transparent, conductive carrier surface, forming a homogenous thin film. They call it SURMOFs. This process is well suited for continuous manufacturing processes and is also appropriate for coating larger plastic carrier surfaces. The MOF thin films are only a couple of hundred nanometers thick, meaning they are just waiting to be used for deformable components, to coat clothing material or as highly flexible solar cells.
The current, popular solution for solar energy is to use expensive silicon solutions as photoactive solar cell layers, but with an increasing demand for the use of sunlight converted into electricity, the world is looking for organic based, cheaper processes – just like the porphyrine-MOFs!
Image: Stephan Ridgway