Hi Guro! And congratulations with defending your PhD! Now we are curious, what have you been doing during these three years?

In my PhD I have worked with purification of silicon for use in solar cells. In order to make a solar cell with high efficiency we need very, very clean silicon, and getting it so clean requires a relatively large amount of energy. There are of course methods to do this today, but it is important to find ways of purifying silicon that are less energy intensive, to reduce the energy payback time for solar cells even further. An important step in this purification is to go from a silicon-containing gas such as silane (SiH4) to solid silicon. By heating the silane gas, it decomposes and releases hydrogen, in a process called pyrolysis. So, in short, my PhD work was about obtaining a better understanding of pyrolysis of silane, and how we can use that understanding to develop better and less energy consuming processes to produce highly pure silicon for solar cells.

Where did you do this work?

I have done my work on the silane laboratory at IFE, where I have been fortunate enough to be allowed to work with a great team of scientists and engineers. Silane is an explosive gas and burns spontaneously in contact with oxygen in the air, so we rely on a large and complex infrastructure to conduct such pyrolysis experiments under controlled conditions. My PhD has also been associated with work package 1 in FME SUSOLTECH.

Sounds good, did you also work with other people in FME SUSOLTECH?

We have had regular meetings with the others in the work package. It has been a little difficult to work closely with those working on metallurgical silicon purification (mainly in Trondheim), since the two activities are relatively far apart from each other professionally, but it has been useful and interesting to see what others in the Centre are working on. Also it is of course motivating to know that there are industry partners who are interested in the work we do.

So, what did you find out?

Perhaps the most important thing is that we have developed a very good measurement setup to measure the various chemical compounds that form at the beginning of this silane pyrolysis process, and no one has been able to do just that before. This has been a very good toolbox to measure and understand what is going on inside the reactor. One important thing we found out through this is that so-called cyclic silane molecules are important intermediate steps on the way to solid silicon, and we think we can use this information to adjust the reactors to, for example, make many small silicon particles or try to avoid making particles at all.

Can you say something about who this is important for?

These results are important for the part of the industry that works with various types of alternative silicon reactors, such as fluidized bed reactors (FBRs). It can also be important for new types of batteries, for example in the production of the electrodes, which can also be made from silicon. In the battery case, we would normally aim to make small particles of controlled size, preferably nanoparticles, so the reactor must be run in a different way than when we make raw material for solar cell production.

 

Ok, what did you like best about doing a PhD?
I really liked that there was a lot of freedom, time and resources to “nerd down” into the depths of a big problem. It’s a bit like a jigsaw puzzle, and it was fun to be able to find old scientific papers which turned out to be useful for what we’re trying to understand, and then have time to put together different pieces of knowledge to find out something new. It’s important to have enough time to dig deep into a so-far unsolved problem in order to be able to move further!

And on the other hand, what did you like least?

Freedom is probably what I liked both the best and the least with PhD: You can work as much or as little as you want all the time and you have a large responsibility for your own progress and working towards reaching big, difficult goals, which of course can be difficult at times. But as I said, I was lucky to have a good team around me at IFE within this field!

(Discussion with first opponent – It seems like this is going well!)

 

Now you arrived at the finish line, what did you think about the PhD defence?

It was actually surprisingly fun, and I can recommend other PhD students to look forward to their disputation! It was of course a lot of work to prepare for the trial lecture and the defense, but I think it went very well. After all, the biggest task was to finish the work in the lab and write the papers and the thesis, so the PhD defence itself is really just a nice price at the end.

So, what are you going to do now?

I have been fortunate enough to be allowed to continue at IFE in a Post Doc position, where I will continue to work with silicon and solar cell technology. This time it will however be in a different place in the value chain, namely material quality in ingots and wafers. I will still have a lot to do with the FME Centre, this time in work package 2, and look forward to working with both the research questions and the people during the next years as well!

(Guro together with colleagues from the IFE silane lab celebrating the PhD defence)