Charge separation in organic solar cells
The use of ultrafast laser spectroscopy enables us to directly measure charge separation in organic solar cells. Since organic semiconductors are molecular (rather than crystalline) in nature, electronic charge pairs produced by photon absorption are inherently difficult to separate. In fact, based on our present understanding of charge separation, it is surprising that organic solar cells produce photocurrent as effectively as they do.
Our work to better understand charge separation on extremely fast timescales will guide the development of new materials for low cost solar cells.
We are also using a combination of new data acquisition and data analysis procedures to overcome technical challenges and improve the sensitivity and resolution of data outputs.
Exciton transport in organic solar cells
When light is absorbed by organic semiconductors, photoexcited electrons exist as tightly bound charge pairs called excitons. In organic solar cells, excitons must be transported to charge separating interfaces during their sub-nanosecond lifetime to enable the electron to escape and a current to flow.
We are using laser spectroscopy to investigate novel ways of enhancing exciton transport that are inspired by photosynthetic light harvesting in plants.
Conjugated polyelectrolytes have potential as photo-active materials. They feature the conjugated polymer backbone necessary for light absorption but have ion pairs tethered to sidechains, which give the material different electronic properties and enhanced processing properties.
In this project, we are exploiting the interaction between the ions and electronic charges to create optical and electronic responses that differ from regular conjugated polymers. In particular, we are investigating how ionic effects can be used to improve the efficiency of organic solar cells.
Nanostructured organic semiconductors
The functionality of organic semiconductors is enhanced when they are assembled on the nanoscale, owing to the short length scales of charge- and exciton transport. We are developing simple solution-based methods for preparing conjugated polymer nanoparticles to use as the building blocks of solar cells.
We are also investigating simple methods for making novel multilayered structures which are constructed by sandwiching different materials together.
Biofunctionalisation of conjugated oligomers for use as electronic biosensors
In this project, we are working to develop highly sensitive electronic biosensors and self-assembled nanoelectronic devices. These materials are made by ‘hybridising’ molecular semiconductors with short peptides and oligonucleotides to create new materials with wide-ranging properties.
Biosensors are molecules that react to the presence of a specific compound by producing a measurable optical or electrical response, and are constructed by attaching or incorporating biological recognition elements into the molecules.
Nanoelectronic devices can be self–assembled from molecular semiconductors into a desired structure based on the template provided by the peptide.
Our research is supported by the Royal Society of New Zealand's Marsden Fund and the MacDiarmid Institute for Advanced Materials and Nanotechnology.
Available Research Projects
Research projects for postgraduate students in all of our research areas are now available. Please contact Dr Justin Hodgkiss for more information.