By combining copper, zinc, tin, and sulphur or selenium, all abundant and low cost elements, the University of Luxembourg has produced a solar cell with 6.1 % efficiency.

The Laboratory for Photovoltaics of the University of Luxembourg has developed an improved preparation process for kesterite solar cells, which resulted in a new European record efficiency of 6.1 percent.

The efficiency has been certified by the Fraunhofer Institute for Solar Energy Systems, one of eight labs in the world that is authorised to certify solar cell efficiencies.

Kesterites combine the low cost of thin film solar cell technologies with extremely low raw material cost. Their main component consists of copper, zinc, tin, and sulphur or selenium, all abundant and low cost elements. 

Several labs have reported that the loss of tin during preparation limits the ability to control deposition processes. The Laboratory for Photovoltaics has therefore developed a preparation process that allows controlling the tin loss and has in the first attempt led to the record efficiency. Details of the preparation process have been published in the Journal of the American Chemical Society. 

"With this first success we are now able to understand the further limitations of these solar cells. This will help us to improve the efficiency further" says Susanne Siebentritt, head of the Laboratory for Photovoltaics. This laboratory was founded in Luxembourg in April 2007 within the framework of the TDK Europe professorship, a public-private partnership funded by TDK Corporation and the University of Luxembourg. 

Thin film solar cells are currently significantly increasing their market share, because of their low production cost. These are mostly based on considerably lower material and energy consumption compared to conventional wafer technologies. 

The Laboratory for Photovoltaics of the University of Luxembourg is a group of researchers developing new materials and processes for solar cells. The laboratory also focuses on furthering the physical understanding of the materials and interfaces involved in these solar cells.