Printed organic solar cells were initially one of the most promising technologies in the printed electronics landscape. However, the ability to transfer the results from the lab to manufacturing was part of the reason that the technology never reached the mainstream. Today, some companies are having some success in the field of organic photovoltaics (OPV).

However, the growing interest in sensors and the need to create energy harvesting systems is increasingly important. That is where Epishine comes in.

With an eye on sensors, consumer electronics and other indoor applications, Epishine just released its first commercial product. Its light energy harvesting modules (LEHs) are a thin and flexible organic solar cell that can reduce or eliminate the need for batteries. It is encapsulated in recyclable plastics and printed using roll-to-roll processes.

“The optimal markets for our light cell are, for example, remote sensors and small displays that today are powered by disposable batteries, but are growing in numbers in a way where it is becoming unmanageable to handle all the maintenance related to battery replacements,” said Jonas Bergqvist, Epishine’s CTO and co-founder.

A spin-off company from the research group Biomolecular and Organic Electronics (Biorgel) at Linköping University, Sweden, Epishine was formed in 2016 by six co-founders, Prof. Olle Inganäs and a group from the Biorgel research team, Bergqvist, Anders Elfwing and Thomas Österberg, together with the entrepreneur Mattias Josephson and Emma Woxlin and Jonas Karles, who worked with Epishine during their last year at Chalmers School of Entrepreneurship.

Bergqvist noted that the work at Biorgel led to a new method to manufacture all-printed organic solar cells using organic PEDOT: PSS-based electrodes. After several iterations with different electrodes and processing techniques, the group could show that by coating and printing half the solar cell stack on one PET substrate and the other half on another PET substrate and then laminate the two halves together, the problems with shunting when using PEDOT:PSS electrodes could be eliminated.

“The initial business model of Epishine circled around cell phone chargers,” Bergqvist said. “Soon we realized that the lamination technique we had developed had the potential to enable a high performance and high yield production of OPV for indoor applications.”

Bergqvist reported that the key aspects of Epishine´s organic light energy harvesting (LEH) modules are high performance even at very low indoor lighting, flexibility and possibility for designed integration in products, which enables larger areas for light energy harvesting, and as a result of using PEDOT:PSS, Epishine has also significantly reduced dampening of the radio signal if the antenna in the connected sensor is placed behind the light cell.

“This way, an even larger area of the product can be used for the energy harvester,” he noted. “Those three aspects interact to a tipping point for many cases where it will be possible to power devices with light even in corner cases with very dim light.”

Epishine’s work with organic solar cells has proven very high performance at low light. The key aspect of Epishine’s organic photocell is that it is all printed from solution. All layers, including the current collectors and electrodes, are either printed or coated from solution in roll-to-roll processes.

“By using the lamination technology mentioned above, we can avoid shunting and produce indoor PV with a high performance at large volumes,” said Bergqvist. “This way we also control all the process steps and can reduce the climate impact further by avoiding sputtered layers.”

Epishine has overcome many challenges to create its light cell, including its ability to scale into large volumes.

“There have been many challenges during the development process, starting with finding the process conditions and materials to be able to process high-performing indoor PV modules in ambient air,” Bergqvist observed. “An initial idea was to place the coating and lamination processes in an inert environment, but being able to solve this enables a very much simplified processing and development.

“Further, the alignment of the laminated foils has been a real challenge to set up at an industrial process and we have also had to work hard to stabilize the coating and printing processes,” Bergqvist added. “Along with establishing the production process, the lifetime and mechanical durability have been a key challenge. Here we are really happy to see the outcome of our accelerated lifetime tests that gives us good confidence that our LEH modules will match the product lifetime in the applications we target.”

Bergqvist noted that the development focus has been to get a product out to the market as soon as possible and then start to improve the features such as reducing cost and further improve the power conversion efficiency.

“In addition, the process yield and sourcing of materials along with shifting the mindset in an innovative team devoted to R&D to move in to focus on quality have been a challenge, where we have been fortunate to have highly skilled advisors to allow us to progress at a good rate,” Bergqvist added.

Bergqvist said that Epishine’s light energy harvesting modules could easily replace small batteries.

“We have a very easy feasibility test to check if a product is a good match for considering our product: Do we speak about indoor electronics with small batteries that last for a year or more? Then you should look closer at Epishine’s light cells,” Bergqvist concluded.