Massachusetts Institute of Technology (MIT) researchers have used genetically engineered viruses to achieve a significant efficiency boost in a light-harvesting system used in solar cells.
Nature has had billions of years to perfect photosynthesis, which directly or indirectly supports virtually all life on Earth. In that time, the process has achieved almost 100% efficiency in transporting the energy of sunlight from receptors to reaction centres where it can be harnessed-a performance vastly better than even the best solar cells.
One way plants achieve this efficiency is by making use of the exotic effects of quantum mechanics-effects sometimes known as "quantum weirdness." These effects, which include the ability of a particle to exist in more than one place at a time, have now been used by engineers at the MIT to achieve a significant efficiency boost in a light-harvesting system.
The researchers at MIT and Eni, the Italian energy company, achieved this new approach to solar energy not with high-tech materials or microchips-but by using genetically engineered viruses. According to MIT professor Seth Lloyd, in photosynthesis, a photon hits a receptor called a chromophore, which in turn produces an exciton-a quantum particle of energy.
This exciton jumps from one chromophore to another until it reaches a reaction centre, where that energy is harnessed to build the molecules that support life. But the hopping pathway is random and inefficient unless it takes advantage of quantum effects that allow it, in effect, to take multiple pathways at once and select the best ones, behaving more like a wave than a particle. This efficient movement of excitons has one key requirement: The chromophores have to be arranged just right, with exactly the right amount of space between them. This, Lloyd explains, is known as the "Quantum Goldilocks Effect."
That's where the virus comes in. By engineering a virus that MIT professor Angela Belcher, has worked with for years, the team was able to get it to bond with multiple synthetic chromophores-or, in this case, organic dyes. The researchers were then able to produce many varieties of the virus, with slightly different spacings between those synthetic chromophores, and select the ones that performed best.
In the end, they were able to more than double excitons' speed, increasing the distance they travelled before dissipating-a significant improvement in the efficiency of the process.
The research was published in the journal Nature Materials.