Polymers for Solar Energy Applications: Exploring Charge Carriers with Raman Spectroscopy and Electrochemistry

Semiconducting polymers are important in organic photovoltaics, photocatalysis, and other energy applications. The stability of organic photovoltaic devices is a critical factor limiting their commercialisation, but structural origins of the primary degradation mechanisms remain largely unknown. This project will identify specific structural changes that occur in the charged polymers (the active species during photovoltaic operation) in combination with known degradation factors such as oxygen and water. In turn, this will enable the design of new, more robust materials. Identification of specific degradation mechanisms will benefit not just the organic photovoltaic field, but also many other applications where such polymers are utilised: light emitting diodes in display technology, for example.

To explore these degradation mechanisms in semiconducting polymers, electrochemistry and Raman spectroscopy will be combined to create the powerful but seldom-used spectroelectrochemical resonance Raman. This technique is not only highly sensitive to small changes in molecular structure and conformation, but also allows the selective probing of a single species in a system with multiple co-existing species. This project therefore aims to apply this novel technique of spectroelectrochemical resonance Raman to a series of conjugated polymers to ascertain specific structural changes during electron transfer, in order to elucidate their degradation mechanisms. A direct outcome of this project will be the creation of design rules to alleviate degradation in organic photovoltaic materials. As such, this project aligns directly with EPSRC's Energy theme, tackling the research areas of Materials for Energy Applications, Chemical Structure, and Electrochemical Sciences.