Tossing worn-out solar panels into landfills may soon become electronics waste history. Designing a recycling strategy for a new, forth­coming generation of photovoltaic solar cells – made from metal halide perovs­kites – will add a stronger dose of environmental friendliness to a green industry, according to Cornell University-led research. A new study shows substantial benefits to recycling perovskite solar panels, though they are still in the commercial deve­lopment stage. “When perovskite solar panels reach the end of their useful life, how do we deal with this kind of electronic waste?” said Cornell researcher Fengqi You. “It is a new class of materials. By properly recycling it, we could poten­tially reduce its already low carbon footprint.”

“As scientists design solar cells, they look at performance,” You said. “They seek to know energy conversion effi­ciency and stabi­lity, and often neglect designing for recycling.” Last year, You and his laboratory found that photo­voltaic wafers in solar panels containing all-perovskite structures outperform photo­voltaic cells made from state-of-the-art crystalline silicon, and the perovskite-silicon tandem – with cells stacked like pancakes to better absorb light – perform excep­tionally well. Perovskite photo­voltaic wafers offer a faster return on the initial energy investment than silicon-based solar panels because all-perovskite solar cells consume less energy in the manu­facturing process.

Recycling them enhances their sustaina­bility, as the recycled perovskite solar cells could bring 72.6 % lower primary energy consump­tion and a 71.2 % reduction in carbon footprint, according to the scientists. “Lowering the energy needed to produce the cells indicates a significant reduction of energy payback and green­house gas emissions,” said doctoral student Xueyu Tian. The best recycled perovskite cell architecture could see an energy payback time of about one month, with a carbon footprint as low as 13.4 grams of carbon dioxide equi­valent output per kilowatt hour of elec­tricity produced. Without recycling, the energy payback time and carbon footprint of new perovs­kite solar cells show a range of 70 days to 13 months, and 27.5 to 158.0 grams of carbon dioxide equi­valent throughout their life cycles.

Today's market-leading silicon photo­voltaic cells can expect an energy payback period of 1.3 to 2.4 years, with an initial carbon footprint between 22.1 and 38.1 grams of carbon dioxide equivalent emissions per kilowatt hour output. “Recycling makes perovs­kites outcompete all other rivals,” Tian said. Informed state and federal policies, along with recycling infra­structure development strategies, can further mitigate the environ­mental impacts in making photo­voltaic solar cells. Said You: “The real value of an effective green perovskite solar panel industry may rely on a recycling program.” (Source: Cornell U.)

Reference: X. Tian et al.: Life cycle assessment of recycling strategies for perovskite photovoltaic modules, Nat. Sustain., online 24 June 2021; DOI: 10.1038/s41893-021-00737-z

Link: Systems Engineering, College of Engineering, Cornell University, Ithaca, USA