Shedding light on the energy capacity of materials
5 mars 2019
As a child, Tomas Edvinsson was fascinated by what happens when light interacts with matter. Today, he researches energy interactions between light and materials for applications in new-generation solar cells, solar fuels and water treatment.
It’s all based on light. So is the research at Tomas Edvinsson’s lab within the Solid State Physics Division, where instruments that measure light fill the rows of benches. In the lab, researchers use laser beams to measure the chemical compositions and energy levels of different materials. Some of the most advanced instruments are the Raman microscopes for Raman spectroscopy, each with a capacity of up to five laser wavelengths. By using blue light in these microscopes, scientists can achieve a resolution of up to 200 nanometres, or 200 billionths of a metre.
“To give you an idea of the size, it’s like making around 300 measurements along the diameter of a strand of human hair. Raman spectroscopy is very useful for measuring how monochrome light is absorbed and induces vibrations in a material and it can even be used to measure under the surface of water or if the material has a voltage spanning it,” says Tomas Edvinsson.
“It allows us to learn how materials behave in different environments and in particular how we can modify materials to optimise their energy levels and thus their properties for a particular application.”
For even more accurate measurements, his research team use light in combination with nuclear spectroscopy. This involves the researchers projecting laser light across a tip-induced plasmon or a small particle of gold. This excites the electrons in the particle of gold and they begin to oscillate in time with the vibrations of the light.
“This creates a near field of downwards of 10 nanometres at the material surface. Which allows us to see things that are smaller than the wavelength of the light and we can even combine the techniques so that we can learn more things.”
The materials that the researchers are studying are selected for their dimensional and electronic properties. One of the main types is metal oxides for photocatalysis, which in combination with UV radiation breaks down micro-organisms. Another is metal halides with various crystal structures and dimensions for use in hybrid perovskite solar cells. What they have in common is that they are interesting for a variety of energy and environmental applications. Many of the research team’s projects involve national projects from the Swedish Research Council, the Swedish Energy Agency, and Formas as well as international corporations.
One is the EU’s PECSYS project (Technology demonstration of large-scale photo-electrochemical system for solar hydrogen production), which aims to use sunlight to split water into solar hydrogen and oxygen. The end product is hydrogen, a renewable and storable source of energy. Besides Tomas’s colleague and solar cell researcher Marika Edoff, the project includes Uppsala enterprise Solibro, and Enel Green Power, an energy corporation that owns Italy’s largest solar panel factory.
“There's friendly competition within the EU project over who has the best water splitting units,” says Tomas Edvinsson. “The photo-electrochemical system which has shown the most promising results at the halfway point of the EU project will be scaled up to 10 m² and placed outdoors in Germany for six months to see how much hydrogen you can get out of it.”
With two years left of the funding period, the researchers have managed to achieve an efficiency level of over 12 per cent from solar energy to hydrogen. But the electrolysis part that Tomas Edvinsson’s group is responsible for has considerably higher efficiency in small units. They have also managed to replace the expensive, rare metals iridium and platinum.
“To be able to scale up the method to a large-scale solution for humanity, we need cheaper, more readily available materials. We now have a number of promising candidates in the form of nickel- and iron-based catalysts for example. In one of the catalysers, we achieved between 83 to 95 per cent efficiency from electricity to hydrogen gas and actually beaten platinum on the hydrogen gas side.”
The research team is still looking for answers to the question of how such good catalytic properties might be retained and utilised in large-scale systems over several decades. “But with these high efficiencies, it starts becoming more promising to save solar and wind energy in solar fuel,” says Tomas Edvinsson. One area of application he has in mind is in fuel-cell vehicles, another is in off-grid storage and heating, maybe even powering industry.
But as a researcher, it is difficult to pursue further development of these ideas unless he leaves academia and starts up his own company.
“The question is: what we are going to choose. Continuing to research difficult new problems and improve the results even further? Or should we just apply for patents and devote ourselves full-time to business activities? With our published articles, at least the results are out for the whole world to see and the market to use.”
Another project in which his research is a vital link is in the field of water treatment using sunlight and photocatalytic materials. In Edvinsson’s lab, water samples from Kenya are exposed to laser light in combination with copper oxide and zinc oxide as photocatalytic materials. The materials are fabricated in the form of tiny, 3-8 nanometre quantum dots. By changing the size of the dots, the researchers can control the energy levels of the materials and how efficiently they absorb light. This makes it possible to treat water to remove chemical and biological pollutants.
“The equipment needed for analysing this is very advanced – lasers and synchrotron radiation facilities. But once we understand and know what is happening, all we need to do is mix up a powder of the materials. This is then brushed or sprayed onto a glass or plastic substrate, which is then immersed in the water in a PET bottle for example. A few hours in sunlight on a tin roof and the pollutants are degraded. If there are heavy metals in the water instead, we look at materials that turn them into larger particles by means of reduction reactions, and these particles can then be easily removed by a filter in the neck of the bottle.
There is no doubt at all that knowing about everything from electrochemistry to quantum physics is essential for his area of research. And it took a number of years before Tomas Edvinsson landed on his feet. In 2002, he received his PhD in physical chemistry at Uppsala University and then taught pharmacists in the Faculty of Pharmacy mathematics and the theory of electrolytes. After 18 months, he switched to the University of Gävle and its Creative Media Lab: “I programmed tilted graphics in small displays so that they had room for more information”.
In 2005, he began as a postdoc with Uppsala University’s Professor Anders Hagfeldt, researcher in physical chemistry, and then moved with that research team to the Royal Institute of Technology (KTH). Together with the world’s biggest chemicals company, BASF AG, this research team filed 6 patents in solar cell materials. Via a position as a research assistant at Uppsala University’s Materials Chemistry unit, Tomas Edvinsson became a senior lecturer in solid state physics in 2015. From there, he was promoted to professor in 2017.
“So my career path hasn’t been what you would call straight as an arrow.”
Despite his seemingly limitless talents, Tomas Edvinsson is modest about his achievements.
“I just keep pushing on and learning new things all the time.”
He also manages to fit in lecturing in a number of courses, including a basic course in solid state physics and a new course in semiconductor optics that he is involved in developing.
“And I also teach the course Nanomaterials in Energy and Environmental Applications, in which the students learn to treat contaminated water with quantum dots that they have developed themselves and also to make solar fuel from water.”
FACTS TOMAS EDVINSSON
Title: Professor in solid state physics at the Department of Engineering Sciences, Uppsala University
Family: Wife and three children, aged 18, 16 and 8.
In his spare time: Besides spending a lot of time with my family, I play bass in two bands. In the band Fat Cotton, we play blues, jazz and Jimi Hendrix. We’ve had gigs in Switzerland and Los Angeles in connection with visits connected with science and conferences. We have also been played on radio in Argentina. Uppsala Professor Per Hansson plays guitar and sings and Professor Anders Hagfeldt, who now lives in Switzerland, play drums. The other band, Lapsed Souls, mainly performs the band members’ own material.
Likes to read: I enjoy reading Jorge Luis Borges and Wolfgang Borchert, and absurdist literature, especially Witold Gombrowicz. Also Russian short stories, they are a bit more melancholic. A few of my friends and I, mostly physicists, have a book club where we read classics such as Albert Camus. But also more modern novels like those of Lena Andersson and Marianne Fredriksson.
Hidden talent: I can throw a javelin, I used to be an athlete a long time ago. 60 metres is my personal record. I competed in and won a few local and regional championships for Upsala IF, a local football club.
Strength: I can cope with having many things on the go at the same time.
Weakness: Having too many things on the go.