Inspired by nature

Through billions of years of evolution, life on Earth has found intricate solutions to many of the problems scientists are currently grappling with. Physicists at the University of Cambridge’s Cavendish Laboratory are trying to unravel nature’s secrets to develop new energy-generating technologies for a more sustainable future.

Focusing on the ancient green sulphur bacteria, research fellows Dr Alex Chin and Dr Nicholas Hine are investigating the early stages of photosynthesis – the process in which plants and some bacteria capture the sun’s light energy and convert it into chemical energy, or food.

“The light-harvesting states of photosynthesis are highly efficient in many species, and happen extremely fast – within a nanosecond, if not picoseconds,” said Chin. “We’re very interested in that efficiency and how it’s managed. Biology has evolved phenomenally subtle systems to funnel light energy around and channel it to the right places. It has also become incredibly good at building tiny devices that work with high efficiency, and at replicating them millions of times.”

Green sulphur bacteria are found in places with very little light, including at the bottom of the oceans, and have existed for billions of years by harvesting light extremely efficiently in order to photosynthesise. Chin and Hine are trying to discover the intimate detail of the bacteria’s clever solutions to capturing and converting light energy. “The idea is to tease out what the trick is,” said Chin. “We’d like to learn, understand and in some sense copy this in artificial systems.”

“Light harvesting is one area where evolution has produced systems that take advantage of quantum mechanics,” said Hine. “I simulate the materials involved from first principles. If you know where the atoms are, you can describe the system using only what we know about quantum mechanics.”

“We need to know about the molecular arrangements to identify the properties that lead to this high efficiency,” added Chin. “I use Nick’s simulations as input into a model I can set in motion, to see how energy will flow.” By working together, the pair is developing an understanding of this photosynthetic system, from where each individual atom is positioned to how the whole system functions.

The idea is to generate broader design principles for new nanomaterials that can be used to build better types of photovoltaic device, or solar cell. “Once we understand the system, we can then move into synthetic chemistry, solid state physics and materials science, and see if we can mimic it,” said Chin. “This may be in a simpler way, but hopefully a scalable one that is useful for industry.”

“Ultimately we want to make devices that harvest the maximum amount of the available sunlight,” said Hine. “Existing materials, like the solar cells on people’s roofs, only absorb about 20% of energy from the sun to turn into electricity. The trick is to make sure the material is tailored to absorb all the energy it possibly can. This way, solar panels become an increasingly attractive source of sustainable energy in the future.”

“Most current ways of building photovoltaic materials have been arrived at to a great extent by chance,” said Hine. “We’re taking a step back and asking whether we can work out from simulations how well materials are going to perform. The materials science of the last century was focused on bulk materials, but now it’s all about introducing structure on a smaller scale.”