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An international team of researchers has developed a novel way to remanufacture fully encapsulated perovskite solar cells after recycling. Researchers claim that the devices can reach 88% of the original products efficiency.
A group of scientists has developed a novel method to remanufacture perovskite solar cells (PSCs) with carbon-based electrodes (CPSMs). They describe remanufacturing, as opposed to mere recycling, as combining reused, recycled, repaired or replaced parts to make a new product.
“In this work we demonstrate for the first time a strategy for remanufacturing perovskite solar cells encapsulated in glass,” they say. “Our study presents a simple experimental method to remove the edge sealant, encapsulant, back electrode, and degraded perovskite, allowing device components to be reused.”
Initially they investigated which materials in a module are associated with a high environmental impact. The module they analyzed - which they say has high commercialization potential - includes a front electrode of fluorine-doped tin oxide (FTO), compact and mesoporous titanium dioxide (c-TiO2 and m-TiO2, respectively), carbon dioxide of zirconium (ZrO2) and a rear carbon electrode. The device is encapsulated with thermoplastic olefins (TPO), a polyisobutylene (PIB)-based edge seal, and a glass backsheet.
“Only a small part of the contribution to the global warming potential (GWP) of the cell stack comes from the materials themselves (5%), while the majority originates from the energy and solvents used to deposit these layers” , they claim. “The main GWP reduction can be achieved by reusing or recycling glass (front and back), which can potentially reduce the GWP of PSMs by up to 53% and 52%, respectively. “The components of photovoltaic cells (and their embodied energy) contribute relatively little to the global carbon footprint.”
The academics also determined which components were worthwhile. First, they heated the cell from 120ºC to 140ºC, to facilitate the mechanical separation of the glass from the FTO backsheet. They then let the glass substrates cool to room temperature before removing the encapsulant.
To dissolve the TPO and GDP encapsulant, they placed them in acetone for an hour and peeled them off. Then, they immersed the devices in a bath of methylamine (MA0) and ethanol to liquefy and wash the perovskite, the part most likely to deteriorate in the shortest time.
“The elimination of perovskite and carbon allows the metal oxide layers (TiO2, ZrO2) deposited on the FTO to be reused to remanufacture encapsulated CPSCs,” they explained. “The morphology and thickness of the layer are preserved. Therefore, carbon deposition and infiltration of perovskite solution, followed by encapsulation with TPO and GDP can be performed again to complete the remanufacturing loop.”
Although the recycled solar cell had a power conversion efficiency of 11.7% after the remanufacturing process, it retained 88% of the original efficiency. Given the efficiency and resources required for the process, this represented a 24% reduction in GWP. If the process is optimized further, and the PCE remains the same after remanufacturing, the decrease in GWP can reach 33%.
“Note that, although total reuse of parts constitutes 62.4% of GWP, the reduction in GWP (compared to virgin modules) due to remanufacturing is substantially smaller,” the researchers note. “This is due to the additional processes required for remanufacturing. Predominantly, chemical treatment in baths of MA0/EtOH and acetone, but also temperature-assisted mechanical separation of glass substrates and annealing at 400 ºC give rise to non-negligible CO2-eq emissions.”
The researchers also determined that the CO2 footprint of electricity generated by remanufactured systems could be lower than that of c-Si. Under the conditions of Freiburg (Germany) and an annual generation of 1,429.2 kWh/m2, the remanufactured system needed 10.7 years to have lower CO2 emissions per kilowatt-hour than the c-Si modules. This contrasts with the more than 16 years of the virgin modules used. If the efficiency of perovskite photovoltaics reaches that of c-Si modules, the footprint of remanufactured modules will be smaller after five years.
“The remanufacturing strategy uses solvents and treatments that do not break down the inorganic components of the devices, such as metal oxide layers,” states the academic group. “Thus, this approach can also be applied to a wide range of nip devices and some inorganic pin-based devices, for which we expect similar GWP reductions.”
They presented their findings in “ Remanufacturing Perovskite Solar Cells and Modules -A Holistic Case Study,” recently published in ACS Sustainable Resource Management . The research group consisted of scientists from the Fraunhofer Institute for Solar Energy Systems (ISE) in Germany, the University of Freiburg and the Philipps University of Marburg, Solaronix in Switzerland and the Federal Polytechnic School in Lausanne. Researchers from Energy21 (Netherlands), the University of Cambridge (United Kingdom) and Abdelmalek Essaadi University in Morocco also participated. |
