Presentation

Take a form, add a function, and you have created something new and unique: a form-function hybrid, a working structure. And if the function is made of a conductive polymer, and the form is of biological origin you can create totally novel materials.

My research, as part of the Biomolecular and Organic Electronics group at Linköping University, consists of two main fields: organic solar cells and self-assembling of conductive polymers.

Main research interests:

  • Self-assembly of conductive polymers
  • Organic solar cells

Self-assembling polymers

Normally humans produce artefacts by taking a larger, previously existing, structure and saw, grind or cut it into shape. A table, for example, is made from the larger structure of a tree. Any assembly is made from already altered, cut down, structures, such as boards. Human manufacturing processes have historically been based on this top-down approach.

Nature, in contrast, creates from the bottom-up - a foetus, for example, starts with a single cell. Cells themselves duplicate by adding nanoscale molecules that enable them to split into more cells. This is the type of creation that I and my colleagues try to emulate.

A molecular bottom-up approach

Starting with macro-molecules our process relies on supra-molecular forces to create larger structures. In layman's terms we mix two elements to create a more complex third element. This kind of production method is resource effective, environmentally friendly, and doesn't use any unsound solvents or precious process equipment. The process is self-organizing, and spontaneous in the right conditions. And it can add function to almost any form.

The non-conductive carriers we use range from the nano-scale, such as protein wires, DNA and lipids, to common macro structures, such as silk threads or paper. Onto these we apply PEDOT-S based polymers, which self-assemble to add a function: the ability to add electronic properties to almost anything.

An experimental research approach

As of yet, my PEDOT-S polymer research has taken a clear experimental focus on material physics. I am an experimenter, struggling to create something in order to understand it. To quote Richard Feynman: "What I cannot create, I do not understand". In my research group we go by the motto that if we can show that it works, we can get an idea of how it works, a strategy that has yielded a number of publications during the years, some before my time.

Sample PEDOT-S research advantages:

  • Self-assembly enables a molecular bottom-up process mimicking nature.
  • PEDOT-S self-assembly enables cheap creation of nanoscale structures.
  • Flexibility and ease of creation makes it possible to utilize a trial-and-error approach to yield unexpected results.

Organic solar cells

Solar cells are environmentally friendly for consumers, but silicon solar cells are resource and energy intensive to produce. A joint Dutch-American study (Fthenakis, Kim and Alsema, 2008) showed an energy consumption of a quarter of a million Wh for 1 square meter of silicon solar panels produced, giving an energy "payback" time of several years.

Organic solar cells, on the other hand, require very little energy to produce. Thus they are more environmentally friendly than silicon solar cells.

Enhancing the solar cell market

In our research group, we believe that organic solar cells have the potential to enhance the solar cells market, as they're lightweight and transparent, enabling mounting on any number of surfaces, including windows, facades and, as they are flexible, sails or clothing.

They are also rapidly approaching the effectiveness of silicon solar cells, and can be manufactured using standard printing press technology - a single, small scale printing press can produce several hundred square meters of organic solar cells per day.

Emergent technology

However, the technology is still emergent, and there are still problems. The stability of organic solar cells is lower than that of their silicon counterparts. Field tests show a lifespan ranging from several months to several years, as compared to 20+ years for silicon.

The efficiency is also lower than for silicon, around 7 % in the field and pushing 13 % in laboratory conditions, compared with 15 % or more for silicon. My contribution to this problem lies in light management techniques. As our organic solar cells are semi-transparent, it is possible to utilize the transmitted light to increase efficiency.

50 % increase in efficiency

By placing a plain piece of paper behind an organic solar cell, it is possible to increase the cell's efficiency by up to 50% by capturing the transmitted light which will scatter back into the solar cell. This is very beneficial since paper is cheap, ecological and recyclable. Thus a cheap solar cell combined with a cheap scattering layer makes for an efficient, yet still cheap and environmentally friendly, product, and we have the patent for this production process.

We are currently conducting trials together with the Tekniska Verken energy company in Linköping using printed organic solar cells.. Our trial modules are currently meter-long, of varying colours, and we are seeing continuous efficiency improvements.

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