Scientists have developed a new technique to recover pure silicon from end-of-life solar cells.

The high-value silicon recovered with the novel process can be sold and reused in new devices. 

Currently, to recycle a solar power module, the highly toxic chemical hydrofluoric acid is used for separating silicon from the cell by removing the anti-reflecting coating, silver, lead, and p-n junction.

Now, scientists from India’s KPR Institute of Engineering and Technology have replaced the corrosive acid with three different chemicals: a 10 M solution of sodium hydroxide (NaOH) applied to the aluminum for five minutes at 63 degrees Celsius, followed by a 6 M solution of nitric acid (HNO3) to remove the silver electrodes and lead, and finally a solution of 90 per cent phosphoric acid was used to remove the anti-reflecting coating based on silicon nitride (Si3NA4) for 45 minutes at 70 degrees Celsius.

The researchers say that the new technique can deliver recycled silicon with a purity of up to 99.9984 per cent. 

The estimated cost of recycling a 1 kg solar cell with this process is US$69. The total profit after recycling a 1 kg solar cell is calculated to be US$185.4. 

The recovered silicon can then be used to manufacture new solar cells, as well as electronic components such as diodes, transistors, and microchips.

More details are described in the paper “Recovery of Pure Silicon and Other Materials from Disposed Solar Cells,” published in the International Journal of Photoenergy.