Sweden-based maker of thin-film solar manufacturing equipment Midsummer has developed a process to recover leftover rare metals such as indium and gallium when producing copper indium gallium di-selenide (CIGS) solar cells.
The process, developed in cooperation with Sweden's Chalmers University of Technology, recovers 30%-40% of the material that is left from the sputtering targets and what ends up on the masks in the machine.
An important feature of this process, Midsummer says, is that it removes selenium by oxygen and thus makes it easier to process the remaining oxidized metals. The benefit of this approach is that selenium may create toxic gases in some reactions.
‘Normally, when recycling these kinds of materials, you usually melt down the materials unrefined," says Sven Lindstrom, Midsummer's CEO. ‘But this new and unique method is far subtler as the process makes it possible to remove all the selenium before dissolving the material in its components with various acids.’
Lindstrom points out that gallium and indium are expensive rare earth materials and the new process makes it possible to reduce manufacturing material costs, while at the same time conserve limited resources.
Midsummer has recently developed a process for producing cadmium-free CIGS on stainless steel with sputtering.