South Korean Team Turns Old Solar Panel Silicon Into High-Value Ceramic

A South Korean research team has developed a method to upcycle silicon recovered from end-of-life photovoltaic (PV) modules into silicon nitride, a high-value ceramic used in the automotive, aerospace, electronics, medical and energy industries for its strength, thermal stability and wear resistance. “To the best of our knowledge, this is the first demonstration of converting silicon recovered from actual end-of-life PV modules into silicon nitride,” corresponding author Jin-Seok Lee told pv magazine.

The team worked with a single end-of-life Suntech solar module containing 54 silicon cells. After removing the glass, frame and backsheet, they milled the material and tested different milling speeds to see how each affected impurity removal. The recovered silicon then went through a two-stage acid treatment: 20 minutes in hydrochloric acid to remove aluminum, copper, tin and lead, followed by 30 minutes in nitric acid to dissolve silver, with a sedimentation step to remove titanium dioxide from the backsheet. The purified powder was then heated in a nitrogen-hydrogen atmosphere, first at 1,350°C for one hour and then at 1,450°C for 10 minutes, converting it into silicon nitride.

The researchers found that milling speed strongly affected impurity removal: severe particle clumping at 800 rpm left a residual aluminum concentration of 4,290 parts per million after acid treatment, compared with just 189 parts per million at 400 rpm. The highest-purity powder, achieving 99.95% purity, came from the 400 rpm batch. “We were impressed by the effectiveness of the relatively simple sedimentation process,” Lee said.

Lee said the team's next step is to move from proof-of-concept research toward a practical, scalable process, working with Korean PV recycling company Wonkwang S&T to develop mobile recycling technology that can process end-of-life panels closer to where they are generated. Lee said this approach aims to cut transportation costs by about 30% and carbon emissions by more than 10%, compared with conventional centralized recycling.