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27 July 2009


Luxemburg’s first thin-film solar cells reach 12% efficiency

The University of Luxembourg’s laboratory for photovoltaics (LPV) has produced its first compound semiconductor thin-film solar cells, reaching 12% efficiency already.

Thin-film solar cells are considered to be much cheaper than silicon-based solar cells because they need much less material and energy in their production, but their efficiency is much lower (a theoretical maximum efficiency of about 20%, compared with 44% for crystalline silicon-based solar cells). The University of Luxembourg’s cells are based on copper indium gallium diselenide (CIGS) and made using a process with what is reckoned to be the potential for the highest performance. Of all the available thin-film technologies, solar cells based on CIGS have shown the highest efficiencies in research and in production, the laboratory says.

In addition, the laboratory is developing new materials and processes for solar cells. The researchers have also produced another solar cell based on a new cheaper material that does not contain costly indium, made by a low-cost galvanic process. This cell reached an efficiency of just 3.2%. This is already close to the record for a cell based on this material (and prepared by a similar low-cost process) of 3.4%.

Currently, the laboratory produces the absorber and buffer layers of the solar cells, explains professor Susanne Siebentritt, head of the laboratory. “But, for completing the solar cells, we rely on the help of our colleagues from Helmholtz-Zentrum Berlin,” she adds. The luxembourgish laboratory focuses not only on the development of solar cells but also on furthering the physical understanding of the materials and interfaces in them.

The laboratory for photovoltaics (LPV) was founded in April 2007 within the framework of the TDK Europe professorship, a public-private partnership funded by TDK corporation and the University of Luxembourg. “We have just a few months ago moved into our new labs,” says Siebentritt. “This allows us finally to start the solar cell preparation. These are really our first solar cells and they have already reached competitive efficiencies.”

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