New Fabrication Method Creates Ultra-Thin Transparent Silver Films for Solar Cells

A new fabrication method for transparent ultra-thin silver films has been formulated by scientists at Ruhr-Universität Bochum and the University of Wuppertal. The material may aid in developing very efficient solar cells and light-emitting diodes. However, traditional chemical approaches have not been able to create ultra-thin and pure silver films. A team led by Professor Anjana Devi and Nils Boysen from the Bochum-based research group Inorganic Materials Chemistry, in partnership with the group of Professor Thomas Riedl from the Chair of Electronic Devices in Wuppertal, published an article on a new synthesis technique in the journal “Angewandte Chemie”. The paper was published online on September 27^th, 2018.

New precursor chemistry

“Precursors for the fabrication of ultra-thin silver films are highly sensitive to air and light,” explains Nils Boysen. The silver precursors can be stabilized using phosphorus, fluorine, or oxygen. “However, these elements contaminate the thin films as well as the equipment used for the production,” continues the scientist. In the course of his Master thesis, Boysen and his colleagues came up with an alternative solution to address the issues related to standard silver precursors.

The scientists developed a chemical silver precursor, where the silver is surrounded by an amide and a carbene, which is even stable without elements such as phosphorous, fluorine, or oxygen. They showed that a silver thin film can be applied to an electrode using the new precursor by atomic layer deposition. In the process, the gaseous precursor is conveyed to the electrode and a silver film is placed there as a layer with a thickness of just a few atoms. As it is very thin, the silver film is transparent.

“As the process can be operated under atmospheric pressure and at low temperatures, the conditions for industrial production are quite favourable,” says Anjana Devi.

A chance for highly efficient solar cells and lights

After a series of tests, the scientists demonstrated that the thin silver films produced using this technique are pure and electrically conductive. “As far as process technology is concerned, the successful synthesis of the new precursor paves the way for the development of ultra-thin silver films,” concludes Thomas Riedl. “It constitutes a first step towards the production of novel electrodes for highly efficient solar cells and lights.”

The collaboration between the chemists from Bochum and the engineers from Wuppertal was the key to success.

Anjana Devi, Professor, Bochum-Based Research Group Inorganic Materials Chemistry.