Photovoltaic (PV) solar modules are a mainstay of renewable electricity generation in Europe. In Germany, for example, solar generated power rose from 27 to 50 TWh between 2012 and 2020. But the challenge for developers is ensuring PV systems remain affordable in the face of the rising cost of raw materials. The global PV industry already eats up 15 percent of all silver mined and that figure is likely to increase sharply in line with demand. And with other tech sectors hotly competing for silver, the concern is simply not viable.
The Fraunhofer Institute for Solar Energy Systems (ISE) is already on the case. They’re investigating how cheaper copper could be used to replace silver in multi-layered, heterojunction solar cells, which have a low carbon footprint and higher efficiency. Silver currently accounts for 10 percent of their production cost.
“We have developed a special electroplating process that makes it possible to use copper instead of silver for the busbars,” summarises ISE’s Professor Glatthaar in a . The busbars make up a grid of thin strips across the panel which collectively conduct the direct current generated by the sun’s energy. The new, laser-structured copper contacts are very narrow (less than 19 micrometres), so the light-absorbing silicon layer is subject to reduced shading. This and the high conductivity of the electroplated copper actually improves the electricity yield.
The team made another breakthrough in the electroplating process: they used aluminium as a mask instead of non-recyclable, polymer-based lacquers or laminated foils. The metal forms an insulating oxide layer on its surface which protects the silicon layers. The dual metal substitution makes the whole solar PV production process more sustainable.
The ISE has launched the spin-off PV2+ to bring the cost-saving technology to market more quickly. The project has been funded by the Federal Ministry for Economic Affairs and Climate Action.