A method to recycle silicon wafer from end-of-life photovoltaic module and solar panels by using recycled silicon wafers

This paper details an innovative recycling process to recover silicon (Si) wafer from solar panels. Using these recycled wafers, we fabricated Pb-free solar panels. The first step to recover Si wafer is to dissolve silver (Ag) and aluminium (Al) via nitric acid (HNO3) and potassium hydroxide (KOH), respectively. The next step is to remove anti-reflection coating (ARC) and emitter on the surface by using an etching paste which contains phosphoric acid (H3PO4). Wafers onto which the etching paste was applied were heated for 2 min at 320, 340, 360, 380, and 400 °C. The recycled wafers showed properties with the thickness of over 180 µm, resistivity of 0.5–4 Ω cm, which are almost identical to those of commercial virgin wafers. Furthermore, the solar cells manufactured with the recycled wafers showed an efficiency equivalent to that of the virgin cells. Pb-free solar panels were fabricated with the solar cells by using 60Sn-38Bi-2Ag solder to assemble the solar panels. Thermal cycling test based on the standard IEC 61215 were performed on the solar panels in order to confirm their stability.