Juha Heinonen receives TEK’s and TFiF’s best dissertation award

In his doctoral thesis, an Aalto University alum developed a loss-free radiation sensor which is already on the way to the global market with mass production just getting started.
Juha Heinoselle parhaan väitöskirjan palkinto. Kuva: Jari Härkönen
Juha Heinonen receives TEK’s and TFiF’s best dissertation award. Photo: Jari Härkönen

Juha Heinonen, an alum of the School of Electrical Engineering at Aalto University, has received the Doctoral Thesis of the Year prize awarded by Academic Engineers and Architects in Finland (TEK) and Tekniska Föreningen i Finland (TFiF). The thesis prize was awarded in Helsinki today for the 25th time. Heinonen completed his doctoral studies in the spring of 2022. In his thesis, ‘High-sensitivity photodiodes using black silicon and induced junction’, he worked on a new kind of silicon-based radiation sensor. Production of the sensor utilises techniques that were found to be promising in earlier research on photovoltaic cells.

‘The sensor is based on a nanostructure that reflects no light and therefore appears to be black - i.e. black silicon that is coated with a thin membrane using the Atomic Layer Deposition (ALD) method invented in Finland. The result was an almost loss-free radiation sensor capable of sensing practically every single photon reaching the sensor, be it visible light or higher-energy radiation. This nearly ideal level of sensitivity is far ahead of that of previous sensors and a large part of my work focuses on learning the mechanisms behind record sensitivity’, Heinonen says.

Together with his researcher colleagues Heinonen set up a company called ElFys for the commercialisation of sensors – already before his doctoral dissertation was even complete.

‘The commercialisation of technology is off to a good start, because ElFys has sold sensors already to 58 customers in 14 different countries and mass production is just getting started.’

The path from researcher to entrepreneur

Juha Heinonen's future plans focus on the further development of the promising technology in his own company.

‘The idea began as a small side project in the research group to test if radiation sensors could be made by applying the same techniques that had been previously used in the group to produce photovaltic cells with a record-high operating efficiency’, Juha says.

Even the first measurements of these prototypes proved to be incredibly good with a sensitivity that was better than with any equivalent sensors on the market.

‘Optimising the structure and the production process, enabled me to improve the efficiency further. Meanwhile, a couple of interested potential customers emerged. Among the researchers who had worked on the project we decided to set up a company, even though the work on my thesis was just beginning. I nevertheless concluded that this kind of an opportunity is likely to emerge only once in a lifetime, so I left the paid work I had at the university and became a full-time entrepreneur in the new company.’

Hele Savin, the supervising professor of the doctoral thesis, admits to having been horrified at first by Juha's decision and feared that the work on the thesis would not be completed.

‘Squeezing the entire work together in five and a half years, and without compromising on quality, is definitely worthy of a prize. I feel that the thesis works as a great example for future students to show how it is possible to rise to entrepreneurship and ultimately, to affect the development of our society.’

So how did Heinonen feel about doctoral studies at Aalto University?

‘My path as a doctoral researcher differed significantly from how it usually goes, but in my mind, this is a magnificent example of all the things that doctoral studies may lead to. The research facilities at Micronova are top-notch, enabling high-quality research with the help of the newest techniques, but they can also be used for commercial production. The working community also deserves praise, as the research groups are full of wise, competent, and helpful people among whom I felt I fit in well. Good concrete evidence of this could be that I dared go and establish a company with the people who I met there.’

Each year TEK and TFiF hand out a prize for the best doctoral thesis in the technical field as recognition for a high-quality thesis that has either significantly promoted, or is expected to promote technical expertise in Finland. The scientific and technical novelty value and applicability of the research results are also taken into account. The value of the prize is € 7500.

Our warmest congratulations to Juha Heinonen!

Link to the thesis: 

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