Simulations TU Delft shows how the new top layer of solar cells could be better

Most of the solar panels we have today are based on silicon crystalline solar cells. These are relatively inexpensive and can convert nearly a quarter of the incident solar energy into electricity. Meanwhile, work is also underway on new types of solar cells, but many of them are still very expensive to manufacture. So at the same time, we are looking at how to improve existing solar cells. That is to say: increase the yield without increasing the costs of production.

How high can you go?

Of course, you always have to deal with a basic limit: what is possible according to the laws of nature. Solar cells today cannot capture all of the light, which also consists of different types of light. In theory, 30 percent should be possible. But if you do this with technologies that are also suitable for mass production, you will end up with about 27 percent. Solar cells have yet to achieve this. They are much closer than 20 percent.

If you want to increase the efficiency, then first of all it is necessary to reduce losses: loss of light, but also loss of electricity. Of the two layers in a solar cell, the top layer is the most important and it must fulfill three requirements: it must be transparent, conductive and inert. The latter means: to prevent the goods from being lost. The balance between these characteristics must also be right.

New formula

Now a German research group has created a new recipe for the upper class. One is based on silicon nanocrystals, with very little carbon. They are bringing together once again 4 sublayers laid out with technology already in use, which makes a difference. The group has achieved good results, but they don’t yet understand exactly why and TU Delft can help with that.

Thanks to the simulation models, they were able to explain why it was so successful. They were also able to demonstrate that the yield can be increased a little with a little tweaking. With the German recipe they came out 24 percent, but it could go up to 26 percent. So one percent is less than the practical limit.

Combi model

TU Delft’s model is not only fast – within a few minutes they can simulate which set of characteristics works best – it also combines two different aspects of research. For solar cell modeling you have optical models and electronic models and at Delft they combined them so you get a better picture.

To go from 24 percent to 26 percent efficiency, some in-vitro tinkering is required. To do so, they can take another good look at the production process. So: how do these nanocrystals form. Then you talk about the temperature at which it is placed, or the pressure used. All of these affect how many crystals form and how they look. It can still be manipulated to yield a 26 percent return]

In this audio you can hear researcher Rudi Santbergen from TU Delft. Read more about research here: The simulations at TU Delft help improve the throughput of solar cells. You can find the paper here: High transparency passivation contact material based on silicon carbide for crystalline silicon solar cells approaches 24% efficiency.