Thinking about recycling from the get-go

Roll-up displays and photovoltaic films for façades – organic electronics have a great deal of potential. However, recycling concepts should be in place before the new technology becomes a mass product, recommends materials researcher Christoph Brabec.

Mr. Brabec, together with colleagues from Germany, the UK, and the USA, you have published a paper promoting the sustainable development of organic electronics. Could you tell us a bit more about this?

This technology is being used in more and more products. Displays are currently the largest market; you might be familiar with the terms AMOLED or OLED for TVs and smartphones. And more applications are set to be added in the coming years. To avoid producing unnecessary electronic waste in future, we need to design sustainable solutions for organic electronics today. In other words, we not only need to develop manufacturing processes and properties, but also plan for technical recycling solutions in the laboratory. In 20 years’ time, when a mass market may have developed, it will be too late.

What does organic electronics refer to exactly?

This is a collective term for electronic circuits consisting of organic polymers or smaller organic molecules. Above all, it refers to semiconductors, which are the central building blocks of all digital devices. The conventional variants are largely based on silicon, while the organic ones are mainly based on carbon. There are pure carbon semiconductors such as diamond, fullerene, or graphene. However, the typical variants are heterosystems, which contain elements such as sulphur, fluorine, or nitrogen.

What is the difference between silicon and carbon semiconductors?

Like silicon, carbon-based compounds are available in abundance. In contrast to silicon, which is grown as a single crystal, the organic compounds are chemically synthesized. The process for producing organic electronics also consumes comparatively little energy and is particularly suitable for applying thin electronic layers to large-format substrates. Flexible polymer films, such as foldable or rollable displays, can also be produced in this way, which is much more difficult with silicon. Organic semiconductors can also be printed digitally, which involves them being applied using inkjet printing technology; the cartridge is then filled with organic molecules. Displays for laptops are already being produced in this very fast way. Organic electronics also offer useful properties for photovoltaics.

To avoid producing unnecessary electronic waste in future, we need to design sustainable solutions for organic electronics today. In other words, we not only need to develop manufacturing processes and properties, but also plan for technical recycling solutions in the laboratory. In 20 years’ time, when a mass market may have developed, it will be too late.

What are these properties?

Organic semiconductors are very easy to make transparent. They then absorb infrared light, i.e. thermal radiation, but not visible light. To make conventional silicon semiconductors transparent, they have to be very thin, which reduces performance. Transparent organic semiconductors can therefore theoretically achieve very high performance efficiency. Although silicon generally has a significantly higher efficiency of up to 27 %, organic photovoltaics have already achieved 20 % efficiency in the laboratory thanks to targeted developments of material properties in recent years. For certain areas and applications, organic photovoltaics might even be much more suitable than traditional PV systems.

What are these areas and applications?

For example, façades, windows, or agricultural areas where large-scale electricity generation can be achieved due to the integration of organic photovoltaic systems. Some initial projects have already implemented this. Another emerging market is modules for the power supply of IoT applications, in other words devices connected to the Internet of Things. These are small electronic gadgets and sensors that can be operated without batteries.

And what about the environmental impact?

If you look at the entire value chain, organic solar cells release two to three times less CO₂ than silicon-based ones – and this can be improved upon. One reason for this is that their production involves low energy consumption. In addition, the throughput of the printing technology is very high, which also saves energy. And the weight of the films is very low. This makes the technology particularly suitable for transportation and assembly. You end up with significantly more watts per gram.

But organic electronics are still relatively expensive?

Yes, that’s because there are millions of different organic semiconductors and no single type has yet established itself in practice. As a result, no value chain has been consolidated, which is why production costs are very high. But we assume that this will change. And at this point, it is important to start thinking today about how components made from organic electronics can leave the smallest possible ecological footprint over their entire life cycle.

So what needs to be done?

Many of today’s electronic components are designed in such a way that they cannot be dismantled. The organic electronic components should be designed from the outset in such a way that they are easy and economical to recycle. In other words, the energy and costs involved in recycling must not be higher than those of production. We have to take these aspects into account right from the development stage. The goal is to establish a circular economy.

And how can that be achieved?

Through multi-layer designs, for instance, with components consisting of easily separable layers. It is thus possible to ensure at the design stage that various materials can be easily recycled at the end of their product life. Organic semiconductors are very well suited for this because they can be easily dissolved again in contrast to silicon-based semiconductors. But we should also use substrates, for example, that are either easy to reuse or are also easily degradable. It is also important to ensure that no toxic substances are used in production.

How is your research making a contribution?

At our institute, we are focused on manufacturing processes for organic electronics. We investigate the influence of production on the end result – in other words a finished organic semiconductor – and we also try to optimize the process so that the semiconductor delivers the best possible performance. Other desirable properties include durability and recycling.

How do you go about this?

We build research and development facilities that are controlled by artificial intelligence. For example, if you want a material that has certain properties, the AI tries to find the “simplest” materials that are best suited for this in experiments. It can also optimize the manufacturing process to ensure that the material ultimately has the best possible properties. The AI analyses the data from an experiment and then decides which further tests need to be carried out. And so it goes on until an optimum is reached – for example with organic solar cells that are powerful, durable, and easy to recycle. We thus want to help make renewable energy even more sustainable and significantly more attractive in the future.

The interview was conducted by Janosch Deeg, pictures Martin Leclaire and @EnCN.

Kontakt

Prof. Christoph Brabec

• Institute of Energy Technologies (IET)

Building Helmholtz-Erlangen /
Room 367

+49 9131/85-25462

E-Mail

More Information

Solar TAP

Printed solar cells that are environmentally friendly and flexible are also the focus of the Solar TAP innovation platform, which Christoph Brabec is helping to coordinate.

HI ERN

The Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (HI ERN) investigates and develops material- and process-based solutions for a climate-neutral, sustainable, and cost-effective utilization of renewable energies.