Vacancy-Rich Silicon as a Flexible Thermoelectric Material

Over 15 TW of power is continually lost worldwide in the form of waste heat. Thermoelectric generators (TEGs) offer one method of reducing this waste, by harvesting the heat and using it to create electrical power. While the conversion efficiency of TEG devices is often <10%, the sheer abundance of waste heat, offering a free fuel source, makes TEGs appealing for many diverse applications. This proposal is aimed at thin-film TEGs (active thickness, 1-20 micrometres), forecast to be a core market sector in the future, with the advent of flexible/wearable electronics, and with the increased uptake of sensors, all of which require low-power. If TEGs can be produced at low-cost and with increased functionality (e.g. flexible), their potential is significant to act as a power source for future electronic devices that improve our quality of life. As an alternative to generators, the same thin-film technology can also be used in reverse for small-scale heating/cooling applications, with thin-film modules already used for chip-cooling in high-performance electronics (space, military and aerospace applications). Silicon-based technologies underpin the global electronics industry due to their many practical advantages. These same benefits would extend to TEGs were it not for the poor thermoelectric conversion performance of silicon. This project will undertake pioneering materials work in the area of "vacancy-rich silicon" - essentially silicon with many atoms removed at the atomic level - building on initial work carried-out by us, which has shown vacancy-rich silicon to be competitive with other state-of-the-art thermoelectric materials. The realisation of flexible thin-film TEGs based on vacancy-rich silicon will represent a transformative step applicable to numerous applications, including power generation and heating/cooling within clothing, as targeted specifically by us in co-operation with our industry partners.

Knowledge: The project will contribute to relevant UK academic networks, such as the EPSRC's Thermoelectric Network (EP/L014068/1), and the UK's Energy Harvesting Network. Special attention will be given to dissemination of findings to academia and companies local to Heriot-Watt University by attendance and participation in the Textiles Future Forum network events, which aims to foster knowledge transfer activities between Scottish universities and companies. Dissemination via traditional academic routes such as journal articles and conference participation will also be carried out.
People: The project will combine partners from academia with industry and the European Space Agency. The latter in particular is likely to provide findings that are of public interest, particularly as a technical target is to implement our thermoelectric technology for space suits. The project will therefore look to nurture outreach activities, with a particular objective being to make an application to the UK Space Agency's outreach programme, Space for all - community funding scheme The aim would be to disseminate news of the technologies to a wider audience while interesting young people in Space technologies and the STEM subjects in general. Further to this, regular updates about the project and the ties to ESA as an end-user will be posted on the Heriot-Watt group website, including pictures and videos where appropriate. Any data that is non-specific to the technology being developed (to avoid compromising IP) will be made available to other researchers and the public for download. Similarly results of the project will be doubly employed as a learning tool for MSc Renewable Energy Engineering students at Heriot-Watt. The involvement of ESA will also directly benefit MSc student projects by their direct involvement in project topics.
Economy: A core focus of this project will be wealth creation by developing a technology that our project partners have expressed a commitment to commercialise and/or utilise. The pathway is in place given the ability of academic partners to develop and prove the fundamental concept, Power Textiles Ltd "to assist and advise on the commercialisation of any developed technology" and for the European Space Agency "to use the technology and IP generated". This project has clear potential to generate intellectual property and the plan is to use this by constructing a development pathway to begin as the project ends, as a route to commercialisation.
Society: Building on the above, this project addresses head-on the significant technical and societal challenge of making UK energy use more efficient. With the growing investment in energy efficient technologies, the UK will establish itself as a leader in emerging energy harvesting industries that will form a growing commercial sector across the next decade and beyond. The developed technology will fit-in here, so contributing to this societal goal. As well as this society benefit, advances in wearable electronics and the increased uptake of sensors can lead to an enhanced quality of life for citizens of the UK.