III-V solar cells based on materials such as gallium arsenide, are among the most efficient solar technologies available, with prospects to achieve a 50 % solar energy conversion under concentrated illumination. However, they are expensive to manufacture due to the material costs making them impractical in the competition with silicon for common applications. According to Prabudeva Ramu, the epitaxial lift-off process enables reusability of the substrates thus reducing the cost, while offering new functionalities.
“Most important, such micrometer-thin structures become flexible, an essential feature in the quest for the development of lightweight photovoltaic converters for satellites and aerospace industry,” he says.
Ramu’s work introduces an innovative release process for multijunction III-V solar cells using internal “push-pull stressors” combined with sidewall protection, preventing unwanted etching of Al and P containing layers within the solar cell stack.
“These results bring us close to scalable, cost-efficient production of thin and flexible multijunction III-V solar cells for space and high-end terrestrial applications,” says Ramu.
In addition to process development, Ramu’s study demonstrates integration techniques using inkjet printing and polymer interconnects for building flexible solar cells, showing how microfabrication and printed electronics can work together for sustainable and advanced energy solutions.
Originally from Pondicherry, India, Prabudeva Ramu carried out his research plan at the Optoelectronics Research Centre, a research group part of the Physics Unit of the Faculty of Engineering and Natural Sciences at Tampere University. His research was supported by Fortum Foundation and contributed to Finland’s growing expertise in advanced semiconductor technologies for sustainable energy and space systems.
Public defence on Friday 28 November
The doctoral dissertation of Prabudeva Ramu (M.Tech) in the field of Physics titled Advanced Epitaxial Lift-off Process for III-V Solar Cells will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at 12 noon on Friday, 28 November 2025 at Hervanta Campus, Festia building and auditorium Pieni Sali 1 (Korkeakoulunkatu 8, Tampere).
The Opponent will be Director of Research Dr. Guilhem Almuneau, from the Laboratory for Analysis and Architecture of Systems (LAAS-CNRS), in Toulouse, France. The Custos will be Professor Mircea Guina from Faculty of Engineering and Natural Sciences at Tampere University.
The doctoral dissertation is available online.
The public defence can be followed via remote connection.