MESO-FRET: MEsoscopic SOlar harvesting via Fluorescence Resonance Energy Transfer

The development of solar energy solutions, with photovoltaic (PV) technologies in primis, is of strategic importance for the nation and worldwide, since the societal and economical demands constantly grow and we need to eradicate soon our reliance on fossil fuels.
In the UK, the renewables sector covers about 11% of the total energy consumption and the government is committing to increase this contribution to 15% by 2020 with a large part that is expected to come from solar power. Meeting this target will require the development of technological solutions with increased energy conversion efficiency and at reduced costs for large scale applications.

Solar conversion has a potential that is not being fully exploited yet. Currently used devices, silicon solar cells, have efficiencies limited to 24% and, although already commercialised and available at competitive costs, still suffer from limitations due to the narrow absorption bandwidth and the expensiveness of the solutions adopted to enlarge it, such as use of multi-stacked devices and solar trackers. To make full use of the available potential, in addition to make evolutionary changes to existing PV technologies, new materials for next-generation PVs are needed.

This project targets the development of new light harvesting materials, hybrid systems obtained by inexpensive methodologies that can be used in luminescent solar concentrators (LSCs). LSCs are a viable solution and cost-effective complements to semiconductor PVs that can boost the output of solar cells. They contain luminescent dyes that capture sunlight energy over a large area of the device and concentrate it by wave-guide effects to the edges, where a solar cell is interfaced. Each cell is exposed up to 10 times more of the sunlight that hits it, meaning fewer silicon cells with reduced areas and thus reduced costs. At the same time, increasing the incident photon density, LSCs could increase the electrical power obtained from each cell by a factor of over 40 and the conversion efficiencies of solar panels by 50%. Despite their promise, however, the wide use of LSCs has so far been hindered by the lack of suitable emitters that would cover the full solar spectrum, by self-absorption losses that restrict the maximum possible concentration factor and by the short longevity of the optical components that photo-bleach within a few months of prolonged use.

The proposed research tackles these limitations and aims at designing new solar 'antennae' for LSCs that possess the key requisites of: (i) panchromaticity, to ensure broadband absorption over the solar spectrum, (ii) high harvesting efficiency, by means of an optimal organisation of the dyes that minimises re-absorption losses and maximises energy concentration through the transfer of the harvested energy by a very fast and efficient process known as FRET (Fluorescence Resonance Energy Transfer), the same that is utilised by natural photosynthetic systems, (iii) durability, by encapsulation into a host-guest structure, to enhance stability against photo-degradation and thermal/mechanical stress, and (iv) cost-effectiveness, to render the technology sustainable, through the use of earth abundant materials and self-assembly strategies, which typically require milder conditions than traditional synthesis.

The ambition of this project is to provide a comprehensive approach, where all requirements for efficient light harvesting are met by one material. To enable this, the new antennae are engineered from the molecular scale, using optical components made of earth-abundant elements, and organised into regular structures that reflect the order from the molecular domain to the mesoscopic scale, the space domain up to 1 micron, that is the size of the proposed solar harvesters. Hence, the acronym MESO-FRET.

This project holds a significant potential to impact on the economic progress of the nation on a long-term. It is centred on the development of new energy materials for improved solar devices and, as such, contains aspects of fundamental and applicative knowledge that may influence the societal, economical and academic sectors.

Society: The project is expected to impact on the public perception and awareness in themes that regard renewable and eco-friendly energies, and the science behind the materials used to harness such forms of energies. The progress and the application of sustainable technologies for the generation of energy are constantly growing, if we consider the extended use of solar panels and the public debate on the need to move away from fossil fuels. To reflect and follow the public interest, the proposed research will reach different levels of audience including a non-academic public, such as families, through outreach initiatives and by using cross-cut multimedia resources.

Economy: The development and the diffusion of sustainable energetic solutions such as renewables is of growing importance for the UK and the global economy. Recently, the UK government has committed to the target of powering 4 million homes with solar energy alone by 2020 and the EU photovoltaic market has an annual turnover of £29B, which marks it as a major economic sector. The current research on photovoltaics and solar fuels and their applications for energy production on a large scale suffer from certain limitations. They are mainly due to the problem of obtaining materials with prolonged durability and able to accomplish energy collection efficiently, guaranteeing the necessary operative stability over time. The proposed research aims at contributing to this sector through the search and the discovery of new light harvesting materials, featuring efficiency and durability that are required for technological exploitation on the market. Potential beneficiaries are identified in companies that operate in the energetic sector and are linked to Newcastle University through the support of the North East Local Enterprise Partnership Centre.

Knowledge: The appointment of the applicant is aimed at strengthening research in artificial photosynthesis at Newcastle University, in order to establish its leading role in advancing this field and meeting the energy challenge. The proposed project is naturally aligned with this purpose and is expected to impact on the fields of solar energy, photovoltaics and photocatalysis, in which there are influential groups at both national and international level. Such groups will benefit from the discovery of new solar materials and from the understanding of their functioning mechanisms. Scientific advances within the photochemistry and materials science communities are confidently foreseen, particularly through dissemination of results at conferences and through research collaborations and networking that the Applicant has established with partners in the UK (Warwick, Nottingham) and international (Germany, Spain, Hong Kong, to name some).

People: The proposed research will contribute to the training of two doctoral students, allocated resources to this project that the School of Chemistry has provided. Young and enthusiastic researchers, they will have the opportunity to contribute directly in advancing the progress of energy research. In doing so, they will benefit from the high level of research training provided by the Applicant, including expertise with state-of-art laser spectroscopy techniques. The competences that they will have acquired in knowledge and transferable skills during the project will render them more appealing for future academic careers or industrial employment in the fields of materials chemistry and renewable energies, strategic areas where EPSRC and the UK are maintaining constant investments.