Production of highly efficient thin-film copper indium gallium selenide (CIGS) solar cells is steadily increasing, leading to a concomitant increase in waste materials from manufacturing and end-of-life disposal operations. An acid leaching technology developed at Chalmers University of Technology, Sweden, offers an environmentally sound route to the recovery of the precious metals needed for new CIGS cell devices.

“It is crucial to remove any contamination and recycle, so that the material is as clean as possible again. Until now, high heat and a large amount of chemicals have been used to succeed, which is an expensive process that is also not environmentally friendly,” said researcher Ioanna Teknetzi.

“We took into account both purity and environmentally friendly recycling conditions and studied how toHighly efficient CIGS cells can be deployed in diverse applications, such as on roof tiles. Source: MidsummerHighly efficient CIGS cells can be deployed in diverse applications, such as on roof tiles. Source: Midsummer separate the metals in the thin-film solar cells in acidic solutions through a much ‘kinder’ way of using a method called leaching. We also have to use chemicals, but nowhere near as much as with previous leaching methods. To check the purity of the recovered indium and silver, we also measured the concentrations of possible impurities and saw that optimization can reduce these.”

The process detailed in the journal Solar Energy Materials and Solar Cells can recover 100% of the silver and about 85% of the indium at room temperature conditions.

Following material and chemical characterization, the solar cells placed in a container with an acid solution. Agitation facilitates the dissolution of metals by launching the leaching process. Different metals are leached at different times during the treatment, which can be stopped before all the metals begin to dissolve and thereby enhance purity.

The industrially valuable metals, present as ions in solution, can then be recovered and reused in the manufacture of new CIGS solar cells.

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