Internship at the prestigious École Polytechnique could bring a shift in solar fuel research

The three-month internship at one of the most significant French technical universities is a continuation of long-term cooperation with colleagues from the Physics of Interfaces and Thin Layers Laboratory (Laboratoire de Physique des Interfaces et Couches Minces - LPICM). The experience gained could advance research on solar power at VSB-TUO.  

“I chose this institution because the research at LPICM is at the cutting-edge, not only in Europe but also in the world. I am part of a group that studies, develops and manufactures solar cells based on silicon nanowires. My main focus is on optical modelling and spectroscopic characterisation of materials and structures. This is a complementary activity, as optical characterisation methods are usually non-destructive and by careful analysis of optical data and their modelling it is possible to understand the physical processes that take place in a complex nanostructure,” explained Halagačka, who received the internship as part of the Science Without Borders 2.0 project. This is not his first time as a researcher in France. From 2016 to 2018, he was a postdoc at the newly established Institut Photovoltaïque d'Ile-de-France (IPVF). His research position at that time was half coordinated by LPICM.  

To study the structures of silicon nanowires, the scientist uses microscopic polarimetry, a method based on measuring the complete optical response of the structure to polarized light.  “In the first step, we are  focused on the nanowires themselves, or the solar cell that they make up. Subsequently, we want to move on to a more complex system, solar fuel cells. This is a device that uses solar energy for water splitting, for example. The energy is therefore not converted into an electric current, as is the case with a solar cell, but is directly used to produce fuel that can be stored relatively easily. Solar fuel research is one way to reasonably reduce our carbon footprint in the future without the need for complex installation and technological solutions at the grid level,” he said. Therefore, he said, it is important to understand the energy conversion processes in these structures, to be able to describe what part of the energy will be used for the solar cell and what part will be used for the photocatalysis of water, to be able to balance the energy intensity of these processes, and to prepare and test prototype structures.

The three-month internship is another piece to the puzzle of mutual cooperation between the two institutions. Martin Foldyna, a graduate of VSB-TUO, is working at LPICM as a researcher at the French National Centre for Scientific Research (Centre National de la Recherche Scientifique - CNRS). In the past, the mutual cooperation was also supported by the joint supervision of the doctoral studies of Zuzana Gelnárová (Mrázková), a student of Nanotechnology. Another result of the cooperation are several joint scientific publications.

“Every internship in a foreign workplace is challenging, both in terms of professional and personal life. It is, however, a way to intensively develop cooperation, and to gain new experiences and new ideas. At the Nanotechnology Centre and IT4Innovations, we have complementary technologies that will allow us to study structures for the preparation of solar fuels in the future, not only in terms of the steady-state, but also the dynamics of charge carriers within the structure. That is, investigating the relaxation times of excited charge carriers and their transitions between different energy levels. This is essential for identifying weak points, states where unwanted charge accumulation occurs, and removing or optimising them to achieve higher efficiency,” concluded Halagačka.