The researchers from Heriot-Watt, Oxford, Harvard and St Andrews universities have been looking at organic solar cells, which use organic polymers which are less expensive to produce. However, they are normally relatively inefficient, throwing away around 90% of the power they absorb.
The team has found a way to use interference between the excited states of molecules to stop them re-emitting sunlight, thereby wasting already absorbed energy. This disproves the assumption that absorption and emission of light by molecules must always go hand-in-hand, limiting how efficient solar cells can be.
The breakthrough, published in Physical Review Letters, centres on the discovery that asymmetric structures can outperform identical molecules ensuring more sunlight is converted into electrical energy. This has allowed the team to identify literally thousands of possible pairs of coupled molecules that could be used to improve solar cell operation.
Using quantum mechanics to improve performance
Dr Brendon Lovett, of the School of Physics and Astronomy of the University of St Andrews, explains, "Quantum mechanics can be used to help improve the performance of solar cells, and we have shown that the effect could be harnessed in many different device designs. We are not limited to very specialised choices of material. This really simplifies how to build a quantum-enhanced solar cell, and hopefully we will see one being made in the next few years."
Lead-author Dr Erik Gauger, of the Institute of Photonics and Quantum Sciences at Heriot-Watt University, added, “What really surprised us is that embracing the imperfections that distinguish realistic molecules from theoretical toy models, can lead to better-performing designs. Whilst we understand the physics behind that now, at the outset of the study we expected exactly the opposite.”
The team hopes to see a quantum-enhanced solar cell being made in the next few years.