❝MIT researchers have developed a simple procedure for making a promising type of solar cell using lead recovered from discarded lead-acid car batteries — a practice that could benefit both the environment and human health. As new lead-free car batteries come into use, old batteries would be sent to the solar industry rather than to landfills. And if production of this new, high-efficiency, low-cost solar cell takes off — as many experts think it will — manufacturers’ increased demand for lead could be met without additional lead mining and smelting.
Laboratory experiments confirm that solar cells made with recycled lead work just as well as those made with high-purity, commercially available starting materials. Battery recycling could thus support production of these novel solar cells while researchers work to replace the lead with a more benign but equally effective material.
❝Much attention in the solar community is now focused on an emerging class of crystalline photovoltaic materials called perovskites. The reasons are clear: The starting ingredients are abundant and easily processed at low temperatures, and the fabricated solar cells can be thin, lightweight, and flexible — ideal for applying to windows, building facades, and more. And they promise to be highly efficient.
Unlike most advanced solar technologies, perovskites are rapidly fulfilling that promise. “When perovskite-based solar cells first came out, they were a few percent efficient,” says Angela Belcher…Professor in biological engineering and materials science and engineering at MIT. “Then they were 6 percent efficient, then 15 percent, and then 20 percent. It was really fun to watch the efficiencies skyrocket over the course of a couple years.” Perovskite solar cells demonstrated in research labs may soon be as efficient as today’s commercial silicon-based solar cells, which have achieved current efficiencies only after many decades of intensive research and development.
Research groups are now working to scale up their laboratory prototypes and to make them less susceptible to degradation when exposed to moisture. But one concern persists: The most efficient perovskite solar cells all contain lead…
❝Recognizing the promise of this technology and the difficulty of replacing the lead in it, in 2013 the MIT researchers proposed an alternative. “We thought, what if we got our lead from another source?” Belcher recalls. One possibility would be discarded lead-acid car batteries. Today, old car batteries are recycled, with most of the lead used to produce new batteries. But battery technology is changing rapidly, and the future will likely bring new, more efficient options. At that point, the 250 million lead-acid batteries in U.S. cars today will become waste — and that could cause environmental problems.
❝According to Belcher, recovering lead from a lead-acid battery and turning it into a perovskite solar cell involves “a very, very simple procedure”…The simple procedure for recovering and processing the lead and making a solar cell could easily be scaled up and commercialized. But Belcher and Paula Hammond knew that solar cell manufacturers would have a question: Is there any penalty for using recycled materials instead of high-quality lead iodide purchased from a chemical company?
❝To answer that question, the researchers decided to make some solar cells using recycled materials and some using commercially available materials and then compare the performance of the two versions. They don’t claim to be experts at making perovskite solar cells optimized for maximum efficiency. But if the cells they made using the two starting materials performed equally well, then “people who are skilled in fine-tuning these solar cells to get 20 percent efficiencies would be able to use our material and get the same efficiencies,” Belcher reasoned.
The researchers began by evaluating the light-harvesting capability of the perovskite thin films made from car batteries and from high-purity commercial lead iodide. In a variety of tests, the films displayed the same nanocrystalline structure and identical light-absorption capability. Indeed, the films’ ability to absorb light at different wavelengths was the same.
They then tested solar cells they had fabricated from the two types of perovskite and found that their photovoltaic performance was similar…
Based on their results, Belcher and Hammond concluded that recycled lead could be integrated into any type of process that researchers are using to fabricate perovskite-based solar cells — and indeed to make other types of lead-containing solar cells, light-emitting diodes, piezoelectric devices, and more.
Long term, the approach continues be to find an effective, nontoxic replacement for the lead. Belcher and Hammond continue those studies. Meanwhile, their work has the potential of aiding in recycling toxic materials. RTFA for technical detail.