Formulating MetaVarnish: Defining a binder system towards indelible metamaterial coatings

Context: Silicon photovoltaic cells are by far the most common with >400GW of capacity installed in 2023. But they suffer from an Achilles' heel; they are bound by the laws of physics never to attain an efficiency greater than 31% as silicon’s bandwidth means they only generate electricity across a narrow range of wavelengths. Our technology utilises programmed assembly of biomolecules to template the synthesis of non-linear meta-atoms which interact with the sun's light and shift infrared wavelengths into the red region of the spectrum, so they contribute to electricity generation. This boosts the PV efficiency to a theoretical maximum >38%. Importantly, our technology can be sustainably produced using biomanufacture and is readily integrated into PV manufacture, but also easily retrofitted to existing PVs in the field. By boosting both installed and future capacity, the significant carbon savings will make a meaningful contribution to humankind's journey to meet the UN's SDG7 renewable energy goals, and ultimately net-zero. We have demonstrated design and fabrication of optical metamaterials in the lab (millilitre scale). Funded by Dstl/DASA we have achieved proof-of-concept for biomolecule-templated synthesis of nanoscale metallic resonators that interact with optical wavelengths of light. Our recent BBSRC Breakthrough Award took the first step towards upscale using engineering biology approaches to manufacture our template biomolecules in a bacterial chassis (sub-litre scale). These pilot studies give us great confidence in the technology with techno-economic analysis indicating we can deliver an attractive reduction in levelized cost of energy. Challenge addressed: Our metamaterial may be thought of as an optically-active additive that must now be encapsulated in a “binder”, akin to a pigment in a paint. The requirements for the binder are that it facilitates the transportation of the metamaterial to the PV’s surface, it acts to promote favourable orientation of the resonators and it forms a protective overlayer. These requirements must be delivered without compromising light transmission. The challenge that this bid tackles is the formulation of the binder material system to achieve a family of metaVarnish products to take our metamaterial from the lab to real-world deployment. Collaboration enabled: The award enables a new collaboration between the academic team and the National Formulation Centre at CPI. Elfick & Seviour have backgrounds in Engineering Biology and Electromagnetic Materials respectively, but lack the requisite expertise in coatings and formulations. The fit to NFC’s competences is excellent. We anticipate that this will be a long-term relationship as we re-imagine our metamaterial for different applications and reformulate our coating accordingly, e.g., metaInks for inkjet printing in optoelectronic devices. Aims and objectives: The aim of this Working with Centres Award is to accelerate us from TRL2 to TRL5 through delivery of a multidisciplinary collaboration delivering a PV coating technology. Facilitating rapid, large-area treatment, the material system must meet the challenges identified above with the end-goal of passing accelerated environmental tests prior to deployment in a field trial at the University of Edinburgh's 3MW solar farm. Potential applications and benefits: Whilst framed around silicon-based PVs, our technology can be redesigned to boost performance in any PV technology by harvesting wasted wavelengths of light. The benefits to solar energy sector stand to be considerable as will the contribution to addressing the drivers of climate change. Beyond this, the metamaterial coating has trickle-down applications across myriad domains including optoelectronics and architectural/horticultural/vehicular glasses.