Chinese researchers have created a brand-new method of recycling silicon cells into wafers so they can be recovered intact from items nearing the end of their useful lives. The wafers are surface-treated and purified as part of the recycling process to prepare them for incorporation into new, high-efficient cells and modules.
Dealing with the increasing number of goods reaching the end of life as the solar business matures is already a research focus at colleges and institutes worldwide. Numerous other strategies are being tested, but experts are holding off until the end of this decade when it is anticipated that the volume of products will increase dramatically and allow for large-scale process experimentation.
A significant issue in this situation has been repurposing and processing silicon from end-of-life cells so that it can once again be incorporated into the PV supply chain to create new cells. It takes a lot of energy and a profound understanding of the minor imperfections still in recycled silicon that are different from brand new material.
Some people have previously suggested that shifting this silicon to uses with lower purity requirements is the best course of action. However, a group from the Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion may have developed an alternative that entirely skips the energy-intensive ingot manufacture stage.
The scientists explained:
“Skipping the process of Si ingot production and wafer cutting can save approximately 40% of the cost of PV module production. Nonetheless, there is still a major challenge for the current technologies: regenerated solar cells from recovered Si wafers tend to exhibit a decreased conversion efficiency, which is not acceptable for the current competitive PV market.”
In light of this, the group looked for strategies to salvage silicon wafers suitable for manufacturing high-efficiency cells and modules. First, they demonstrated various chemical processes that clean wafers and enhance their surface properties, enabling their use in brand-new, high-efficiency cells. Finally, to decrease surface reflectance and create “black silicon” wafers, the researchers used a technique already employed by wafer producers.
The group explained:
“Through this technology, desirable and highly pure Si wafers with intact structure, minimally reduced thickness, and excellent light-trapping ability are successfully obtained. In addition, the properties of the reclaimed Si wafers are characterized and evaluated for new solar cell manufacturing and packaging, which encourages regenerated solar cells with higher power conversion efficiency than that of new commercial solar cells.”
A recently released article in Resources, Conservation and Recycling titled “A systematically integrated recycling and upgrading technology for waste crystalline silicon photovoltaic module” details the entire procedure.