Strategies for improving light-harvesting efficiencies of photo-batteries

Photo-batteries are a new solution for harvesting and storing solar energy, where the same electrode material simultaneously harvests sun light and stores it. These devices have only recently gained traction and are therefore poorly optimised both from a solar cell and a battery design perspective. As a result, these devices show limited energy conversion efficiencies, capacities, and cycle life. Nevertheless, these materials are extremely promising for powering off-grid sensors and other autonomous devices as well as to provide energy solutions for rural communities in developing countries. Till now, these photo-batteries have been considered primarily from the viewpoint of charge storage, but not from the angle of light-harvesting which is one of the reasons for their low efficiencies (less than 1%). This project will fundamentally revisit how the photo-batteries are designed by building on the midi-project by drawing inspiration from solar cells and concepts developed by the nanotech community in photo-catalysis and photodetectors. Dye-sensitized solar cells are of particular interest, because of they have an anode, cathode, and electrolyte, just like a battery - so design cues from this class of solar cells will be useful for developing photo-batteries. In addition, dye-sensitized solar cells also provide a solution for creating thick electrodes with a large surface area, which is important for both the battery and solar cell operation. Finally, some of the materials used in dye-sensitized solar cells such a sintered TiO2 and ZnO nanoparticles are used as active anode materials in Li-Ion batteries. Because of the synergies between dye-sensitized solar cells and Li-Ion battery anodes, we anticipate that photo-batteries building on design rules for dye-sensitized solar cells will achieve better energy conversion efficiencies, which is currently the most important draw-back of Li-Ion photo-batteries.

Our main impacts will be:
- a new generation of interdisciplinary nano researchers with expertise across science and innovation, fluent in the combination of approaches and technologies
- strategic developments in the study and control of nano-interfaces connecting complex architectures, for advances in emerging scientific grand challenges across vital areas of energy, health and ICT
- integration of new functional nanotechnologies together by harnessing nano-interfaces within larger application systems, and their translation into innovative products and services through our industry partners and student-led spin-outs
- a paradigm change of collaborative outlook in this science and technology
- a strong interaction with stakeholders including outreach and public engagement with cutting edge nano research
- improved use of interdisciplinary working tools including management, discipline bridging and IT

Economic impact of the new CDT is focused through our industrial engagement programme, as well as our innovation training. Our partner companies include - NPL, Hitachi, Oxford Nanopore, TWI, ARM, Eight19, Mursla, Britvic, Nokia Bell Labs, IBM, Merck, Oxford Instruments, Aixtron, Cambridge Display Technologies, Fluidic Analytics, Emberion, Schlumberger, Applied Materials and others. Such partnerships are crucial for the UK to revive high value manufacturing as the key pillar to lead for future technologies. We evidence this via the large number of CDT projects resulting in patents, with their exploitation supported by Cambridge Enterprise and our Industry Partners, and direct economic impact has also resulted from the large proportion of our students/alumni joining industry (a key outcome), or founding startups including: Echion Technologies (battery materials), Inkling Cambridge (Graphene inks and composites), HexagonFab (2D materials), Simprints (low-cost biometrics), Cortirio (rapid diagnosis of brain injury).

Training impact emerges through not just the vast array of Nano techniques and ideas that our cohorts and associated students are exposed to, but also the interdisciplinary experience that accrues to all the academics. In particular the younger researchers coming into the University are plugged into a thriving programme that connects their work to many other sciences, applications, and societal challenges. Interactions with external partners, including companies, are also strong and our intern programme will greatly strengthen training outcomes.

Academic impact is fostered by ensuring strong coherent plans for research in the early years, and also the strong focus of the whole CDT on study and control of nano-interfaces connecting complex architectures. Our track record for CDT student-led publications is already strong, including 4 Nature/Science, 6 Nature Chem/Nano/Mat, 13 Nat. Comm., with student publications receiving >6000 citations in total, including 16 papers with >100 citations each and high altmetric scores. Students have also given talks and posters at international conferences and won numerous awards/fellowships for research excellence.

Societal impacts arise from both the progression of our cohorts into their careers as well as their interaction with the media, public, and sponsors. We directly encourage a wide variety of engagement, including interaction with >5000 members of the public each year (mostly pre-university) through Nano exhibits during public events such as the Cambridge Science Festival and Royal Society Summer Science Exhibition, and also art-science collaborations to reach new audiences. We also run public policy and global challenges workshops, and will further develop this aspect with external partners. Our efforts to bring societal challenges to students' awareness frames their view of what a successful career looks like. Longer term societal impact comes directly from our engagement with partner companies creating jobs and know-how in the UK.