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US researchers claim breakthrough new solar material

Researchers at MIT and Princeton claim to have found a way to increase the maximum amount of electrical energy released by solar cell. It may be that as much as 35% of all light energy hitting a future solar cell, can be released as electrical energy.

The entire process is a bit like quantum dots on modern television screens which emit different colored light depending upon the size of the quantum dot, and it was explained in articles in Nature and repeated in Science Daily, and involves putting a layer of hafnium oxynitride, just a few atoms thick, on top of silicon. This layer takes a photon in, but instead of releasing a single electron in response, it releases two new types of particles (excitons) which in turn trigger two electrons once they hit the silicon. The potential is therefore to double that amount of energy it releases, but the article explains that it will not be that efficient and instead it will just increase it somewhat – hence the 35% estimate up from 29%.

This has a few years to go to get into production and represents a divergence in the way research moves forward in solar technology. On the one hand Perovskite research is lowering the price of the materials to release almost as much energy as Silicon, or more usually to work alongside Silicon but using less of it, and on the other, this new approach is increasing the cost of materials, but to release far more energy. Both will begin to hit production in a similar time frame and essentially both will offer a route to making solar energy more cheaply. It may be that concentrated solar energy may reach for this new process, as it suits its aims to have a high release of energy from a smaller surface – and we are assured that technology is making a comeback.

While the chemistry that is being used has been known for years the secret is a class of materials like hafnium oxynitride, which release excitons, which behave quite differently from electrons as they can be cut in half or combined.

So the process goes, absorb an electron, release more than one exciton, and then merge a few of these and use them to stimulate silicon. Controlling this process, and optimizing it for silicon is the next step in the chain, and then the materials need to be stabilized to perform over long periods.

The truth is that the US in particular, and the rest of the world outside of China, in general, all need to get an IPR “leg up” to make it successfully into building solar panels, in a way that they will meaningfully be able to compete with China. It is essential that the US takes a stronger financial interest in renewables, because at present it is badly represented in the technology, and therefore less interested in it than it needs to be.

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