New generation of solar cells

The laboratory for photovoltaics of the University of Luxembourg has produced its first thin film solar cells made from compound semiconductors, already reaching a 12 percent efficiency.

Thin film solar cells are considered the next generation of solar cells and are expected to be considerably cheaper because they need much less material and energy in their production than today’s photovoltaic modules.

Researchers around the globe are racing to develop efficient thin film solar cells. The solar cells made in Luxembourg are based on a semiconductor made of copper, indium, gallium and selenium (CIGS) and made by a process with the potential for highest performance. Furthermore, the scientists of the University of Luxembourg produced another solar cell based on a new cheaper material, which does not contain the costly indium, and made by a low cost galvanic process. This solar cell has reached an efficiency of 3.2 percent. This is already close to the world record: the worldwide best cell based on this new material and prepared by a similar low cost process shows an efficiency of 3.4 percent.

The laboratory for photovoltaics of the University of Luxembourg is a group of researchers developing new materials and processes for solar cells. Of all the available thin film technologies, solar cells based on CIGS have shown the highest efficiencies in research and in production. Prof Susanne Siebentritt, head of the laboratory, explains: “Currently we can produce the heart of the solar cells, the so called absorber layer and the buffer. But for completing the solar cells we rely on the help of our colleagues from Helmholtz-Zentrum Berlin”. The luxembourgish laboratory focuses not only on the development of solar cells but also on furthering the physical understanding of the materials and interfaces involved in these solar cells.

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. This allows us finally to start the solar cell preparation. These are really our first solar cells and they have already reached competitive efficiencies”, Prof Siebentritt says, “I am very proud of my team”.

Photo: Laboratory for photovoltaics of the University of Luxembourg