Photo sourced from: University of Leicester
The innovation is a result of lab experiment with the solar panel, 12×15 centimetres size and 2 grams weight, comprising a silicone plate, 100 micrometres thick, which is on one side coated with a layer of silicon nitride and on the other with a layer of aluminum. Concurrently both sides were fitted with silver electrodes (the conductors, through which electric current leaves a solar cell).
The laboratory specimen during the experiment was firstly placed in aluminum chloride solution, where aluminum electrode was removed from the silicon plate by means of ultra sound. Then, the solar panel was placed in calcium chloride, on the bottom of which under interaction with an oxidiser (ferric chloride), where deposition of silver chloride started. The latter might be converted into metallic silver on the next stage. The process does not damage the silicon plate and anti-glare coating and, therefore, they can be reused.
The experiment participants are planning in the future to expand the new technology usage so that they might extract copper, bismuth (silvery metal with pinkish hue) and tellurium (rare semimetal of the silvery-white colour) from thermoelectric materials, used in perovskite solar cells. Another area of the research will have to be an extraction of nickel and gold from circuit boards as well as rare earth metals (neodymium, dysprosium) from magnet wastes.
The search of methods for the secondary production of materials from the solar panels is gaining more popularity. For example, the French startup Rosi Solar in 2022 suggested extracting silicon, silver, and copper from the solar panels with an aid of the high temperature pyrolysis, which is customarily used for ethylene production (the basic petrochemical raw material) from naphtha and consequent production of polymers. The process, permitting to isolate metals from solar cells in absence of oxygen will allow reducing emissions of carbon during entire life cycle of batteries, considering that the silicon production is contingent upon high volume of CO2 emission in comparison with magnesium, aluminum, and titanium.