“Clean growth [is] at the heart of our modern Industrial Strategy”, promised Energy and Clean Growth Minister, Chris Skidmore, approximately one year ago. This statement came as the UK government launched their ambitious target to “achieve net zero emissions” by 2050. In a ‘net zero’ or ‘carbon neutral’ world, any greenhouse gas emissions produced would be offset by schemes to remove them, such as planting trees or using carbon capture. 

Now, scientists from the University of Sheffield are rising to this challenge. This June, the Department of Chemistry secured funding from the Engineering and Physical Sciences Research Council. This will support a £7.25 million project striving to solve a “grand unsolved challenge” in sustainable technology development. 

The research team comprises chemists, biochemists, and physicists from the universities of Sheffield, Bristol, and Exeter. They’re taking on excitons: tiny energy-carrying particles which are responsible for carrying absorbed light energy through materials.

“Control of excitons is essential for many new and emerging technologies identified in the government’s Industrial Strategy as being vital to the economic success of the UK”, commented project leader, Professor Graham Leggett. 

Solar capture is a fundamental process in green energy production. Currently, 90% of solar cells are powered by silicon semiconductors, which absorb sunlight and convert it into electricity. 

In the seventy years in which silicon-based cells have led solar capture, they have remained expensive and inaccessible for most. Though solar energy is one of the lowest-cost forms of power generation in the UK, withdrawal of government support has recently caused a plunge in installations. Without public support, this renewable energy capture system stands no chance against fossil fuels. 

For solar capture to become prevalent and accessible, a sustainable alternative to silicon must be found. Electronic devices based on sustainable organic compounds are already in the common market – certain smartphones like the iPhone X, for example, contain organic LEDs. However, the materials of these devices do not realise their full energy potential.

If abundant and inexpensive organic materials are to replace silicon, scientists must find a way to ensure that they can match – or preferably exceed – its efficiency. This begins with controlling the movement of excitons. To current knowledge, excitons are only able to move short distances through organic materials. While carrying absorbed light energy, they rapidly recombine and cancel each other. This makes them inefficient energy-transporters, that cannot store light energy effectively. 

That’s where the team’s ambitious new project comes in. Their work will focus on “develop[ing] design rules for the long-range transport of excitons”, says Professor Leggett. Taking inspiration from the mechanisms of photosynthesis, they hope to combine molecular designs with nanostructured materials to create materials in which excitons travel more efficiently. 

The result? Improvements all round for “solar energy capture, photocatalysis, quantum technologies, and the design of diagnostic devices for personalised medicine”, Professor Leggett hopes. In the future, these developments could help reduce greenhouse emissions and support a future of carbon neutrality. 

It’ll take an ‘all hands on deck’ approach for the UK to meet its 2050 zero-emissions goal, and the University of Sheffield is running at the front of the pack with this ground-breaking research.


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