Using block molecules to improve energy transfer in devices
Martin van Son defended his PhD thesis at the department of Chemical Engineering and Chemistry on February 24th.
Every day, billions of people around the world use electronic devices such as laptop computers and smartphones. This leads to significant energy demands, and with the world’s population ever-increasing, this demand will only increase further. One way to alleviate this is to make electronic components in these devices more efficient by reducing the number of defects between the molecules that they are made from. For his PhD research, Martin van Son studied how so-called block molecules can improve energy transfer between molecules found in everyday electronic devices.
Previous research has shown that certain block molecules can improve the ordering of molecules in a device, and thus prevent the development of defects. The block molecules in question consist of an active component coupled to a short chain with which it wants to mix.
During his PhD research, Martin van Son investigated these block molecules can improve energy transfer between adjacent molecules and therbey increase energy transfer efficiency. To this end, he addressed some fundamental open questions about the molecular design of these block molecules and took the first steps towards applying these molecules in devices involving light.
Regarding the molecular design, van Son and his collaborators found that both the active component and the side chains they attached to make block molecules should have a similar radius. This leads to the most favorable molecular packing of the block molecules.
The relative radius can be tuned by varying the number of side chains attached to the molecule. van Son found that crystal structures can be used to design the block molecules. Furthermore, he showed that mixtures of strongly interacting active components can be used to change the color of the material, or the efficiency with which the materials can emit light.
For the potential application of block molecules, van Son focused on energy transfer in the form of light. Usually efficient energy transfer is only possible with isolated fibers or bulk materials such as crystals. However, the block molecule approach allowed for highly efficient energy transfer in processable materials.
Furthermore, this energy transfer is both directional and occurs over significantly longer distances than reported for most organic molecule assemblies. This makes block molecules interesting for transistor applications.
Different block molecules were studied to improve the efficiency of solar cells. Through a series of energy transfer steps, light that cannot be absorbed by solar cells due to its low energy can be boosted to have sufficient energy such that it is absorbed. This helps to increase the efficiency of the solar cell. Compared to unordered molecules, these energy transfer steps can be enhanced 100-fold with the ordered block molecules.
Title of PhD thesis: Functional block molecules with nanoscale order. Supervisors: Bert Meijer and Ghislaine Vantomme.
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