Epishine’s organic solar cells are based on carbon, not silicon. The thin-film cells can be printed like newspapers – and may end up being the cheapest method to produce electricity, ever.

Solar cell technology has become more affordable, and interesting alternatives have emerged alongside the traditional silicon solar cells. One example is Epishine, a company working to commercialize an innovative solar cell that consists of very thin sheets of carbon atoms, printed on flexible plastic film.

Life cycle perspective is important

Epishine has developed a solar cell with nanolayers of light-absorbing polymers printed on PET film. Photo: Epishine.

More and more people choose to install rooftop solar panels, and Sweden has doubled its capacity in the last couple of years. Still, the increase is from a very low base. The first solar cells were put into place in the 1970s, but at that time they were used mostly for lighthouses, boats, summer cabins and caravans. There is still a market for such facilities, but the steadily growing segment is grid-connected solar power. Most people would agree that solar contributes to a better environment – but how does it really fare in a life cycle perspective?

”Future energy sources have to be scalable and cost-efficient, without depending on limited resources. They should be recyclable and free from hazardous chemicals,  with a small climate footprint from manufacturing. Our organic thin film solar cells satisfy all these requirements, and have many advantages over silicon-based conventional systems”, says Emma Woxlin, Epishine’s Market Director.

Solar cells printed on plastic

”Imagine a sheet of plastic, one millimeter thick, with the actual solar cell printed on the surface. The plastic is PET and the solar cell does not contain any metals. We are talking about organic solar cells. The light absorbing polymers are printed in nanoscale on top of the plastic film. Like plastic ink printed on plastic paper”, Emma Woxlin says.

”We are still the only company that are able to produce metal-free solar cells with high surface coverage. We can achieve that thanks to our production process which is similar to newspaper printing. We can make the solar cells very long, and they have the potential to become the cheapest method of energy production ever. Two transparent electrode materials surround a light-absorbing polymer layer with photoelectric properties. The solar cells can be connected in series, and the power is delivered by metal electrodes at the outer edges”.

The solar cell technology is the result of 25 years of research and development, from laboratory experiments to printable process. One of the initiators is Olle Inganäs, Professor of Biomolecular and Organic Electronics at Linköping University. He is regarded as a pioneer in the field, and was one of the first in the world to grasp the technology’s potential when the first experiments were conducted in USA and Japan in the early 1990s.

”Printed organic solar cells is a resource efficient and climate beneficial product”, says Emma Wohlin, Epishine. Photo: Epishine.

The printing facility is located at Printed Electronics Lab in Norrköping. It has an annual production capacity of 20 000 square meters of solar cells. Epishine aims to have commercial production in place at the facility within a year.

”The material is transparent, flexible and can be produced on roll. This makes it attractive in many applications, such as protective window coatings that generate electricity. It can be integrated in building materials as a decorative surface. The cells are thin and easily carried or transported. A roll of solar cells could act as a portable power generator where there is sunlight available. They can also be used for indoor energy harvesting”, Emma Wohlin says.

Internet of Things

”The light, thin and flexible solar cells have optimal properties for integration with small things, and can power connected sensors and similar that are on their way through the Internet of Things development. Our results already indicate that we will have better performance indoors than silicon-based solar cells, even though we are still at early stages of optimization”, Emma Wohlin says.

”Organic solar cells maintain efficiency better than silicon solar cells in low-intensity light. Sensors that for instance monitor heat or moisture or trigger alarm systems require energy, and wiring them to the electricity grid or replacing batteries may be too complicated to be feasible. We can power sensors by harvesting light energy where they are placed. Solar-powered wireless sensors in stores and industry settings would be easier to install and maintain. Such sensors need a couple of hundred microwatts of power, which matches what our modules can provide”.

”Organic solar cells have many advantages. We estimate the energy break-even time to be less than a month. For silicon-based solar cells, the break-even time is at least a year since both the silicon extraction and the manufacturing consumes a lot of energy. Another advantage is that the organic modules can be recycled pretty much like a PET bottle. Nevertheless, there are still hurdles to cross and we need to improve the efficiency, lifespan and large-scale production methods further. The people on our team are competent and experienced, and we have real hope to be able to come up with smart products that contribute to a more resource-efficient world”, Emma Wohlin says.

In 2017, Epishine was nominated as one of the most promising tech companies in Sweden by the technology and financial newspapers Ny Teknik and Affärsvärlden. Their motivation was that “Epishine AB has developed a method to print organic solar cells. The technology makes it possible to power sensors in the growing Internet of Things wirelessly. In the future, this new kind of solar cells may even provide millions of people with affordable renewable energy”.

The article was published in November 2017.