Exploiting quantum and phonon interference for molecular thermoelectricity and Seebeck sensing (MoQPI)

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In any electrical device, unwanted heat produced by electronic components is usually wasted. A thermoelectric device can convert this waste heat to electricity through Seebeck effect. Generation of electricity from heat via the Seebeck effect is silent, environmentally friendly and requires no moving parts. Unfortunately current thermoelectric materials are difficult to process, have limited global supply and are not sufficiently efficient to meet the requirements of current energy demands. That is why there is a world-wide race to develop materials with a high thermoelectric efficiency. To realise a high-performance thermoelectric material, both electron and phonon transport should be optimised. Since both electrons and phonons (vibrations) behave like waves, they can exhibit interference phenomena at a molecular scale, which could be used to optimise their transport properties. Therefore simultaneous control of room-temperature quantum interference (RTQI) of electrons and room-temperature phonon interference (RTPI) have the potential to underpin new design strategies for efficient molecular thermoelectricity. This proposal, entitled 'MoQPI,' aims to design new highly-efficient thermoelectric materials for converting waste heat into electricity, by exploiting RTQI and RTPI in cross-plane (CP) sub-10nm thin films. Cross-plane structures are advantageous, because they do not suffer parallel heat paths through the substrate and can be engineered to suppress parasitic thermal conductance due to phonons. The radically-new CP nanostructured materials proposed in this Fellowship will be formed from single-molecules, parallel arrays of molecules in self-assembled monolayers (SAMs) and van-der-Waals (vdW) molecular nanoribbons sandwiched between metallic and/or graphene electrodes. I will exploit RTQI and RTPI simultaneously in many molecule systems and vdW molecular nanoribbons to yield a new generation of high-performance thermoelectric materials. Simultaneous assessment of quantum and phonon interference in molecular-scale thermoelectric materials will elucidate design strategies for the development of new generation of thermoelectric devices and consequently will change the community view on routes to engineer and realize highly efficient thermoelectric materials. MoQPI will also develop innovative applications of the Seebeck effect for discriminating biological sensing. Using the Seebeck coefficient for sensing is advantageous compared with current methods based on electrical sensing, because two biological species that might possess similar conductances could have Seebeck coefficients with different signs or magnitudes. Furthermore, the electrical conductances of biomolecules such as DNA nucleobases are extremely low, which is problematic for conductance-based sensing, but advantageous for Seebeck sensing, since low electrical conductances typically lead to high Seebeck coefficients. Seebeck sensing using single molecules and molecular nanoribbons proposed in this proposal will generate ground-breaking knowledge needed for next-generation biosensing. MoQPI will also explore hybrid molecular structures for energy harvesting. The identification of simultaneous RTPI and RTQI enhanced energy harvesting and molecular sensing in ultra-thin-film molecular layers is the first step to realise new types of quantum technologies with important societal and economic impacts in the real world.