Optimizing the electronic properties of molecules based on optically or electrically active organic building blocks for device applications means fine-tuning their properties at surfaces. Up to scales of 10 nm, this is no problem because supramolecular chemistry techniques that rely on making molecules interact via non-covalent forces can be employed. However, controlling the properties of such molecules at distances greater than 10 nm is difficult because simple bottom-up chemistry approaches do not work.
Now, Paolo Samori of the University of Strasbourg, France, and colleagues in the Netherlands, Germany, Italy, Belgium and the UK, have developed a new class of macromolecules that could be used to overcome this problem. The molecules, based on poly(isocyanodipeptide), possess a very rigid backbone and side chains that point away from this backbone. Each side chain can be functionalized with a wide range of units, whose position and inter-unit interactions on neighbouring side chains depend on the central macromolecular scaffold. The position of the functional molecular units can be controlled in 2D over a distance of some hundreds of nanometres for the first time.
"The scaffolding approach allows us to achieve full control over the interactions, which leads to tunable electronic properties of the ensemble," said Samori.
As a test, Samori's team successfully fabricated field-effect transistors and solar cells from the material to study how their architecture affects the way the devices work, and how well they work. The researchers used scanning probe microscopy and computational calculations to explore material and device characteristics.
"Such a macromolecular scaffolding approach to locate functional units in pre-defined positions is not just limited to (opto)electronics, but may be extended to many other fields, such as catalysis and (bio)medicine", Samori told nanotechweb.org.
The work was reported in Advanced Materials.