At the laboratory for photovoltaics (LPV) we are interested in the exact mechanisms that reduce the efficiency of real solar cells compared to ideal devices. We focus on the next generation solar cells, based on thin film tandem devices. By studying the basic semiconductor properties of materials and devices we understand the fundamental limitations of actual devices and open ways to move beyond these boundaries.


Thin film solar cells are complex structures with several layers and interfaces, which challenge conventional semiconductor theories. They are not single crystals but consist of tiny micrometer large crystals, the grains, which are tightly linked with each other at grain boundaries. Our research helps understand the effects of these interfaces, grain boundaries and polycrystalline semiconductors on solar cell efficiency. We make highly efficient devices ourselves.

Thin film solar cells are particularly interesting because of their low energy consumption and their low carbon footprint. They can be prepared on a metal or plastic foil and made into lightweight and flexible solar modules.

All solar modules have decreased in price so much in the last years, that now the cost related to the rest of the system becomes the main expense. These costs are area related, therefore it is essential to increase the efficiency of solar cells, because then we need less area to produce the same amount of electricity. Conventional solar cells have been improved over many decades and have come close to theoretical limits. A way out are tandem solar cells, where we stack two different solar cells on top of each other, so that each can make better use of the solar spectrum and the efficiency becomes higher. We investigate semiconductors and solar cells for the use in tandem devices.



Prof. Siebentritt won the 2022 FNR Outstanding Mentor award, see the video here

Watch Prof. Siebentritt explain how we us photoluminescence to make solar cells better at the NanoGe PV school in April 2021

Watch Prof. Siebentritt speak about tandem solar cells at the Molecular Frontiers Symposium in Göteborg in December 2017

Watch doctoral candidate Max Wolter explain in 90s the potential of thin film solar cells


We celebrated 10 years of LPV

The University of Luxembourg celebrated in May 2017 a decade of research successes and positive impacts in photovoltaics and semiconductor physics. A scientific symposium followed by a public lecture and a night of festivities marked this anniversary

Friday 5 May 2017, Belval Campus


In November 2015, Prof. Siebentritt received the “Grand Prix en sciences physiques – Prix Paul Wurth” of the Institut Grand Ducal:

Follow the link for more information : FSTC News 2015


Four current and former members of LPV received the “FNR Award for Outstanding Publication” in 2014:

Follow the link for more information : FSTC News 2014