Ultrathin Silver Films for Solar Cells

The researchers have applied an ultrathin layer of silver on this silicon substrate  e.g. for solar cell electrodes. (Source: Marquard, RUB)

A new fabri­cation process for transparent ultrathin silver films has been developed by researchers at Ruhr University Bochum and the Univer­sity of Wuppertal. The material may help build highly efficient solar cells and light-emitting diodes. However, traditional chemical methods have not been able to produce ultra-thin and pure silver films. A team headed by Anjana Devi and Nils Boysen from the Bochum-based research group inorganic materials chemistry, in colla­boration with the group of Thomas Riedl from the chair of electronic devices in Wuppertal, developed the new synthesis method.

“Precursors for the fabrication of ultra-thin silver films are highly sensitive to air and light,” explains Boysen. The silver precursors can be stabi­lised with fluorine, phosphorus or oxygen. “However, these elements conta­minate the thin films as well as the equipment used for the production,” continues the researcher. Boysen and his colleagues developed an alter­native solution to tackle the problems associated with common silver precursors.

The researchers created a chemical silver precursor, where the silver is surrounded by an amide and a carbene, which is even stable without elements like fluorine, phosphorous or oxygen. They demon­strated that a silver thin film can be applied to an elec­trode with the new precursor by atomic layer deposition. In the process, the gaseous precursor is transported to the electrode and a silver film is deposited there as a layer with a thickness of merely a few atoms. Because it is so 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 Devi.

Following a series of tests, the researchers showed that the thin silver films manu­factured using this method 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 ultrathin silver films,” concludes Riedl. “It constitutes a first step towards the produc­tion of novel elec­trodes for highly effi­cient solar cells and lights.” (Source: RUB)

Reference: N. Boysen et al.: An N‐Heterocyclic Carbene Based Silver Precursor for Plasma‐Enhanced Spatial Atomic Layer Deposition of Silver Thin Films at Atmospheric Pressure, Angew. Chem. Int. Ed., online 27 September 2018; DOI: 10.1002/anie.201808586

Link: Inorganic Materials Chemistry (A. Devi), Ruhr University Bochum, Bochum, Germany