A steady increase in photovoltaic (PV) cell deployment adds to the contribution of renewable energy worldwide but also contributes something undesirable – a growing amount of valuable metals and other components discarded at the end of solar cell service life. The volume of such waste is projected to swell to 60 million to 78 million tons by 2050. An opportunity to recover and recycle precious materials, and thereby shrink the environmental load of PV waste, has been developed by University of New South Wales, Australia, researchers.

As an advance relative to traditional bulk recycling methods, the micro-recycling technology supports the selective recovery and transformation of valuable materials at the microscale. Manual separation of the junction box, cables and aluminum alloy frame is followed by module glass delamination via a previously developed hydrothermal delamination method. A medium-temperature heat treatment at 550° C applied to the waste effectively removes the ethylene vinyl acetate encapsulants and polyvinyl fluoride backsheets.

Heat-treated silicon and untreated silicon fragments are then subjected to chemical etching using potassium hydroxide and nitric acidic media at 80° C. Surface roughness and elemental analyses informed decisions about how long to perform etching to remove aluminum from these fragments. The process described in Resources, Conservation and Recycling facilitated the removal of aluminum impurities within three minutes while avoiding silicon loss. Gold and tin were also removed during the etching stage via an acidic media.

The recovered materials can be upcycled to form silicon carbide wafers and other components for PV cells and microwave absorption applications.