Wednesday, July 07, 2010

Increasing PV efficiency: R&D breakthrough

American scientists capture lost energy

The solar energy falling onto the earth is incredibly abundant but the majority gets lost anyway. So what is the big deal about improving the efficiency of solar cells? Well for starters, highly efficient PV cells could create a complete sea change on the cost, material use, and the amount of land presently employed in harvesting the sun’s energy.

Today, the efficiency limit of photovoltaic cells is approximately 30 percent. For a long time this was thought to be a physical border, as certain high-energy photons in sunlight exceed the band-gap energy in a PV cell. That energy, in the form of so-called 'hot electrons', is too high to be turned into usable electricity and is lost as heat in conventional solar cells.

Well, it seems we had better start referring to that physical border in the past tense. The 'hot electrons' could not be captured — until now.

According to the peer reviewed weekly Journal Science, published on 18 June, a team of material chemists at the University of Texas at Austin and the University of Minnesota have demonstrated that this lost energy can indeed be salvaged and transferred to an adjacent electron-conducting layer. Their experiment, carried out using a system consisting of quantum dots coupled with a titanium dioxide layer, was the first time that this 'hot-electron transfer' has been achieved directly.

Making use of this concept could potentially increase the efficiency of a PV cell to more than 60 percent. A great deal of science and engineering needs to be carried out yet so this does not mean that such highly efficient PV cells are likely to be on the market soon. There are still many barriers to overcome, for instance, how to channel the recovered energy for practical use. However, at the very least, this news provides strong evidence that improving the efficiency of PV cells is not yet even close to its limit.


solar pv panels said...

That capturing "hot electrons" breakthrough is incredible. This should increase overall efficiency of solar panels. That may just be the breakthrough the industry needs to reach critical mass market appeal.

Villette said...

Coupled with solar panels cost going down and solar panels generally becoming more efficient, this can get the renewable energy industry reach critical mass. Bright times ahead.