Organic Solar Cells: The End of Silicon-Based Solar

The dominance of silicon-based solar cells may be ending, as organic photovoltaics have recently achieved a competitive level of efficiency. Scientists have long sought to overcome this hurdle. For consumers, this will usher in cheaper, lighter, more flexible, and vastly more versatile solar panels.

Silicon-Based Solar

Scientists make typical solar cells are made with silicon, which, up until recently, provided the efficiency needed to make them commercially viable. These are made with crystalline silicon, which is used to separate layers of boron, a positively charged material, and phosphorus, a negatively charged material. By doing this, scientists create an electric field. When sunlight hits the silicon, the photons knock electrons loose, allowing them to travel freely in this field, producing an electric current.

This setup generally converts around 15–20% of sunlight into electricity, with the highest amount achieved being at about 27%. Given the fact that the theoretical limit for any solar cell is 33.7% according to the Shockley-Queisser limit, the efficiency of silicon-based solar cells has been hard to match.

Organic Solar Cells

However, scientists have made great leaps with solar cells made with organic materials. That is, scientist make organic solar cells with conductive carbon-based polymers, which, when bombarded by photons, lose electrons. This creates a free, negatively charged electron and a positively charged polymer. Scientist then separate them by a gradient, use them to create a current, and then recombine them. While it is still being debated how exactly this happens, recent advancements have created efficiencies of 17.3%, making them able to compete with silicon-based cells.

The importance of this cannot be understated, as scientists long thought above 15% was theoretically impossible. Scientists achieved this record breaking efficiency by connecting multiple organic cells in tandem, a surprisingly complex process, to compensate for their low absorption rate. This also allows different cells to absorb different wavelengths of light, thus enlarging the range of the electromagnetic spectrum that can be utilized.

Now, with a competitive efficiency rate, manufacturers are excited about the many uses that organic solar cells provide. Because they are so lightweight and thin they can be adapted to virtually any surface. This mean just about anything can have a convenient power source. They are also soluble, meaning scientists can be dissolve them into different liquids and incorporate them into other materials. For example, some have proposed that idea of using them in fabric production, thus opening the door for solar powered clothes. Because of how versatile they are, there is no telling how creatively they will be used.

Some experts have also pointed to the fact that manufacturers can make them “rapidly on thin plastic sheets using established printing processes.” Therefore, the transition to organic solar cells should be smooth, as manufacturing costs can be kept at a minimum.

Research Continues

Although organic solar cells still lag behind the efficiency of silicon-based cells, progress is accelerating.

Researchers from the seven leading research institutions in the US, China and Europe are collaborating. They recently created a theoretical framework for increasing efficiency in organic cells. This group is being led by Feng Gao, a Swedish professor. He claims “We have formulated some rational design rules to minimize energy losses in organic solar cells. Following these rules, we present a range of examples with low energy losses and high power conversion efficiencies.”

This group has also produced a dozen new materials to help increase the efficiency of the organic solar cell.

Moreover, a team from NYU has found a way to weatherproof organic solar cells by making the top layer nonreactive. They did this by stripping electron-accepting molecules from the surface. This makes them immune to water, air, and even light.

Therefore, a new wave of solar products are likely to hit the market in the near future. The days of silicon-based cells seem to be numbered. Overall, this helps achieve a cleaner and more environmentally friendly future.

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