Optoelectronic Nanostructures via Polythiophene Block Copolymer Self-Assembly

Conjugated organic molecules and polymers possess the electronic properties of inorganic semiconductors and metals, while being of lower cost, lighter weight and more amenable to device manufacture. Furthermore, these properties can be readily controlled by manipulation of the molecular or macromolecular structure, which offers a distinct advantage over many comparable inorganic materials. As a result, organic replicas have now found applications as wires, light-emitting diodes, sensors, field-effect transistors, photovoltaic devices and lasers.The optimisation of many such devices, however, relies on either balancing charge carrier transport or manipulating the diffusion of excitons, both of which require control over the supramolecular structure. Unfortunately, the patterning of conjugated organic units into nanoscale objects of predetermined size and shape remains a fundamental challenge. This problem is further amplified by the need for more complex architectures, such as junctions or compartmentalised structures and composites, for the extensive realisation of nanoscale organic replicas of inorganic microelectronic components.

In this collaborative proposal we target proof of concept studies that will permit the development of a new platform for the creation of functional 1-D semiconducting nanostructures based on block copolymers with crystalline, pi-conjugated polythiophene segments. This offers the simplicity of solution phase self-assembly but affords potential control over the dimensions of the structure. Furthermore, this new method also offers exciting possibilities for accessing both compartmentalised and hybrid structures, which should function as key components in a variety of nanoscale devices.

The proposed fundamental research program seeks to develop new routes to self-assembled semiconducting structures, which may ultimately complement current technologies in the construction of diodes and transistors. These devices are key components in virtually every piece of electronic equipment, and so many industries may ultimately benefit from progress towards this goal.

Manufacturers of high-tech electronic components would be the primary beneficiaries of this research with corresponding gains in the economic competitiveness of the UK. Furthermore, the size and global nature of the electronic components end-user community could drive significant R&D investment to the UK were the program objectives to be achieved. The wealth created by both these mechanisms would be expected to have a significant positive impact on the UK economy.

The exploratory and fundamental nature of the proposed research may allow for further opportunities, as we should also be prepared to exploit results that are currently unforeseen. To this end, there may be a role for spin-out companies where results would impact on communities that are less mature than the electronics industry. It should be envisaged that these ventures would also have a positive economic impact on the UK. In addition to the science that this project will produce, it will provide an ideal environment for the training of scientists in state-of-the-art polymer synthesis and solution-phase self-assembly, as well as cutting-edge nanoscale characterisation, time-resolved spectroscopy, and device fabrication. These fields are all currently experiencing rapid growth and individuals with skills in all these areas are likely to be very much in demand.

The solution self-assembly platform that we propose to develop for our aims has benefits beyond the potential to fabricate semiconducting devices. The technique itself relies on the interactions between molecules, which are weak in comparison to chemical bonds. This means that the process often requires little energy and generally proceeds at room temperature, in contrast to the high temperatures required to prepare and purify many typical semiconductors. It may also be transposable to water as a solvent by using hydrophilic blocks. This improvement in the production of these materials would contribute towards environmental sustainability, protection and impact reduction, thus resulting in a positive societal impact. The proposal also has a polymer synthetic component and this is expected to yield new procedures to valuable materials, which are more atom efficient than existing methods. This advance would be associated with lower energy and resource costs. Finally, the platform has potential to yield structures that may display efficient photovoltaic effects, and these materials have been targeted as important sources of clean energy in the future.