Engineering electrochemical devices: Photosynthetic solar cells and high power capacitors

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Electrochemically active materials will be investigated that aim to provide low cost solar energy harvesting - including built-in energy storage, as well as high power supercapacitors. Photosynthetic protein complexes, also known as reaction centres, absorb light and separate electrical charge. The process is performed with near perfect quantum efficiency (almost every photon is converted to charge). The objective is to create solar cells that employ these proteins, or their synthetic analogs, to generate electrical energy with reasonable power conversion efficiency. In principle -based on the electronic states available in reaction centres - ultimate power conversion efficiencies of as high as 27.5 % are possible (with genetic modification). Previous work has demonstrated generation using photoelectrochemical configurations very similar to dye-sensitized solar cells. We aim to overcome serious challenges that have led to efficiencies well below 1 % including the lack of selectively of electrodes and poor light absorption. Our group has proposed unique implementation to overcome these challenges. A novel cell design enables good light absorption and built-in energy storage. A key reason for poor performance are lack of selectivity of electrodes resulting in poor charge transfer kinetics. This will be overcome by employing semiconductor electrodes, in which band positioning favours charge transfer from one mediator and restricts that of the other. With these and other modifications we hope to produce photo-electrochemical cells that demonstrate power conversion efficiencies in excess of 10 %, and store energy over a period of hours. In the longer term it is hoped that the approach will lead to a commercially relevant and environmentally friendly method of producing electrical energy from sunlight.Also proposed is a method of creating fast charging supercapacitors that can replace tantalum capacitors where low internal resistance and millisecond discharge times are required. A novel separator material and porous metal electrodes proposed to achieve this goal.Finally, the program includes the application of novel nanotube yarn based actuator technology, in much stronger than muscle contractions result for low voltage pulses.