A recently completed TDE activity with Germany and the Netherlands, has developed ultra-thin and lightweight solar cells in the hope they can be used to make the first ever European flexible solar arrays.
After cultivating a film of photovoltaic semiconductors through epitaxial growth on Germanium and Gallium arsenide substrates the activity then used two different techniques to lift off the solar cell layers. The two techniques, spalling and epitaxial lift-off (ELO), could be used to remove the active layers of the solar cell and separate them from the substrate, leaving behind thin solar cells.
ELO is a chemical process for removing the active layers of the solar cellsby including an additional layer during the manufacturing that can then be sacrificed. Spalling is a manufacturing process where a material is deposited ono the wafer that induces a crack inside the structure, which can be controlled and is used to remove the active layers of the solar cellsfrom the substrate. For both processes the activity was able to improve reproducibility, processing times and cost.
The activity produced fully operational samples with both techniques, which then successfully underwent reliability testing including thermal cycling.
Overall the greatest achievement of the activity was the know-how gained on the handling and processing of ultrathin layers, including the new methods, tools and materials developed.