New solar technology could dramatically change how we harvest light from the Sun, scientists say

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A new solar technology could help us dramatically change how we harvest light from the Sun, the scientists behind it say.

Solar cells are expected to be one of the major ways that we move towards harvesting energy sustainably and through a variety of new ways. But they are limited by a range of factors, one of the most fundamental of which is the fact that light has to be the right colour to be absorbed by the solar cell, as well as the way they need to be relatively thick to absorb enough light energy.

Scientists hope that it will one day be possible to make a solar cell that is panchromatic, or able to absorb the full spectrum of visible light. It may also be possible to make them thinner, and therefore less bulky and heavy.

Scientists often point to the way that the light-collecting antannae of plants and bacteria work as a model for possible solutions to those problems. But those comparisons are also a warning: they require lots of different dyes to be able to gather all of the energy of absorbed light and focus it.

Now researchers say they have come up with a new kind of light-harvesting system that is markedly different from previous examples, and could help overcome those problems.

It has a structure similar to semiconductors, which allows it to absorb light “across the entire visible range”, said Frank Würthner, from Julius-Maximilians-Universität. But it also relies on the high absorption of organic dyes, which means that it can gather a lot of light energy using a thin layer, like in natural light-harvesting systems.

To work, the system that developers call a light-harvesting antenna takes four different dyes and folds them so that they are stacked closely to each other. Because they are so neatly arranged, they are able to move energy around quickly and efficiently.

They refer to the system as UPRB. That corresponds to the four light wavelengths that are absorbed by each of those folded components: ultraviolet, red, purple and blue.

Taken on their own, those four dyes to gather about one to three per cent of the light energy. But in the new system, used together, they are able to convert 38 per cent of the light into useful energy.

A study reporting the work, ‘Panchromatic Light-Harvesting Antenna by Supramolecular Exciton Band Engineering for Heteromeric Dye Foldamer’, is published in the journal Chem.

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