Free access to the latest research on solar energy

Technical interdisciplinarity is the key word in an online course on plastic solar cells set-up by a research group at DTU Energy for the online educational portal called Coursera.

You probably already know a lot about plastic solar cells! The technology involves many scientific disciplines, so almost regardless of which technical background you may have, you will be able to recognize several of the items used in connection with polymer solar cells.

Chemistry, physics, electronics, materials science, energy production and the environment are just some of the disciplines that you will learn about if you take the online course "Organic Solar Cells - Theory and Practice".

"Solar cells are a very interdisciplinary subject," says Eva Bundgaard from DTU Energy. "For example, if you know much about electronics but have little knowledge of chemistry, or vice versa, it will be a good course for you."

The online course is open for everybody
Having so many concoctions of technical disciplines, it is no wonder that DTU is at the forefront in terms of both research and teaching. Last year over 38,000 participants were interested in the new course.

"It sounds like a lot, but it is really not that impressive. People are surfing Coursera as they are surfing television; that is the norm. A pass rate of five is entirely normal and corresponds to over 1900 people who have followed the course intensely "says Eva Bundgaard, who is one of the four researchers from DTU behind the course on plastic solar cells.

She likes the idea that it is open to all. "If we are contacted by someone who would like to know more about plastic solar cells, we can refer to the course website. Furthermore we are now able to distribute our research to a lot of interested people ".

Online course is free - workshop costs
The actual course is available through the Coursera platform. It is free, so the only thing you need to invest in your learning is time. But if you are further interested in the subject and would like to have the associated workshop, you or your employer must pay up first.

"The workshop is where your knowledge is really put into perspective. The participants have already familiarized themselves with the theory through the online course when they come to the workshop. But you will not really grasp it until you get hands-on experience, and start making and measuring the effect of solar cells. We have some really good discussions in the workshop, and that is where the new ideas and contacts occurs" explains Eva Bundgaard.

The plastic makes electricity
Polymer solar cells live up to their name as they consist almost entirely of polymers. At the top there is a layer with a transparent anode. Underneath there is an active layer, and at the bottom there is a layer that serves as the cathode. When the active layer is bombarded by light waves, free electrons are created, and these migrate down to the cathode creating tension between the anode and cathode.

Compared to other types of solar cells, these solar cells have two obvious advantages. They are cheaper to produce and more environmentally friendly. Production can take place by using e.g. printer technology where the production costs are extremely low compared to previous generations of solar cells.

Environmentally, plastic solar cells are better because they do not require rare metals such as indium or heavy metals like lead, and because they do not require very high temperatures during production.They also pollute much less when they become waste.

However, these solar cells also have disadvantages. "Polymer solar cells are still relatively unstable, i.e. they may already lose performance after two years. Most solar cells that are on the market today have a lifespan of over 25 years, "says Eva Bundgaard.

The benefits outweigh the disadvantages
The causes of the instability are very complex. Polymers are unstable in light, usually caused by UV rays. By encapsulating solar cells with a UV barrier, one can get the solar cells to last longer. The plastic must also be thermally stable, because when the sun shines, the polymers are heated. These are some of the problems that scientists are currently trying to solve.

The advantages are however so significant that they easily outweigh the disadvantages. "Despite the relatively short life span, the low energy consumption during production means that in theory plastic solar cells can pay for themselves several times over their life span compared to current solar cells," says Eva Bundgaard.

The solar cells still need more research and development, and actual commercialization of polymer solar cells is still to come. "Commercial production of plastic solar cells is not very far down the line. So it is good that there are many who study plastic solar cells," says Eva Bundgaard.

The academic content
"One of the great challenges in organizing the course has been to find the right professional level. When there are so many research subjects for the students to learn, it can be difficult to define a high level of standard in all subjects. In some areas, the course is perhaps not quite at master’s level, while it is slightly higher in other areas."

"In general, we have tried to set the level at medium to high in all the subjects, and then we have elaborated on some elements so you can follow up if you find something to be particularly difficult. We have done a lot to that the videos are suitable for both medium and high level. When we employ such an interdisciplinary approach, the student always finds some elements more challenging than other. "

Will the social aspect disappear?
Although many students testify to a massive success for the team behind the course, they can also see the greyer aspects of online education. Educators and students lose the personal contact. Eva Bundgaard however, does not consider this a big problem.

"I would dare to say that very few professors at a basic course with over 200 students are in close contact with each of the students," she explains. "Students in online courses are like any other students. Some are very enthusiastic, while others just follow the program and do some of the tasks ".

One group of students is much larger among online students than among traditional students. In the free online courses there will always be a large group, who are just browsing a topic by seeing some of the videos without taking tests or passing the exam. "But if you acknowledge this fact, you can accept that it is just five percent who pass, as long as the number of participants is so high," says Eva Bundgaard.