CREDIT: Heliatek/Tom Baerwald
Researchers in Denmark recently claimed a major breakthrough in the production of organic photovoltaic (OPV) solar cells. Unlike traditional silicon solar cells, used in rooftop solar panels and large-scale solar farms, OPVs use organic semiconductors — made from plastics and other flexible materials — and are much lighter, more flexible and less expensive.
Because they use environmentally friendly materials and can be produced quickly with lower processing and materials costs, OPVs can be used in much more innovative ways, according to Jade Jones, Solar Analyst with GTM research. The flexibility of OPVs has its proponents thinking of potential uses that never would have been possible — solar cells on electronics, backpacks, clothing, windows. Jones said she’s even heard of researchers talking about using them for curtains.
Organic photovoltaics could be particularly useful in places that don’t see a lot of sunlight, Dr. Fernando Castro with the U.K. National Physical Laboratory recently told The Atlantic. Because they don’t require direct sunlight like traditional silicon cells, OPVs can generate power for a larger portion of the day.
While Castro said it has improved significantly in recent years, the most commonly cited downside of OPVs is the fact that they are less efficient than traditional solar cells. This is what the team at the Technical University of Denmark sought to address by accomplishing the first roll-to-roll manufacture of tandem OPV modules. By stacking the layers on top of one another, they were able to print them out rapidly on a large sheet. The team argued that by spreading the cells over a large area, the lack of efficiency becomes less of an issue.
“If I have made a kilometre of solar cells, then I am not interested if one module has an efficiency of 10 percent and the rest are two percent — I think what is important is what you can make for the public,” Frederik Krebs, head of the research team, told Chemistry World. “I am the guy that makes a lot of it and tries to look for the average and what is practical, and then there are the other guys that look at what is obtainable. Everybody has their role to play and hopefully we will meet some day, probably somewhere in the middle.”
Krebs and his team started the freeOPV initiative, which builds on the concept that polymer solar cells should be made available to anyone interested in them. Krebs encourages anyone with a technical or academic interest in OPVs to “make use of this special offer to study, posses, claim, reverse engineer, copy, and use these OPV modules that have been created to propagate OPV and hopefully enable us to reach the objective of supplying the globe with energy from OPV in the future.”
Another key limitation of organic photovoltaics is the short lifespan, something researchers in Germany are hoping to address by embedding the solar modules in flexible glass to better protect the components. “Glass is not only the ideal encapsulating material, it also tolerates process temperatures of up to 400 degrees,” explained Danny Krautz, project manager at Fraunhofer Institute for Applied Polymer Research. The specialized glass is fracture-resistant, extremely strong, and can be used to make layers that are only 100 micrometers thick — roughly the same thickness as a sheet of paper.
While recent technological advancements could be promising, Jones said it’s important to point out that “there is a difference between commercial cell efficiency and research cell efficiency. A cell produced in the lab will have a higher efficiency than a cell produced at mass scale.”
And until the efficiency and durability of organic photovoltaics is improved, we likely won’t see them produced on a large scale. “OPV is still in the research/working group phase,” said Jones. “We aren’t seeing any big commercial manufacturers talk OPV.”
Nevertheless, citing the vast potential for mass adoption of the technology, the German government recently invested €16 million ($21 million) into the research and development of organic photovoltaics. The project will be spearheaded by Merck, the pharmaceutical, chemical and life science giant, and by developing more stable and efficient OPV materials, seeks to facilitate large-scale deployment for uses such as powering onboard electronic systems in cars and solar-powered glass facades on buildings.