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Scientists at the US University of California, Los Angeles (UCLA) have used an antioxidant known as L-glutathione as an intermediate layer in an organic photovoltaic cell to prevent other materials from oxidizing. The cell has an efficiency of 13.5% and an average visible transmittance of 21.5%. The researchers say it is suitable for applications in solar greenhouses.
UCLA researchers have developed organic solar cells (OPVs) that can power greenhouses while blocking ultraviolet rays to prevent overheating.
“We have already created a startup that will scale up the production of these organic solar cells for industrial use,” researcher Minhuan Wang told pv magazine .
The new device incorporates the antioxidant L-glutathione as a reducing intermediate layer. This facilitates charge transfer between the cells zinc oxide (ZnO) layer and the fabricated photoactive layer, which is made of a non-fullerene acceptor known as PM6:Y6, the scientists explain in “Achieving sustainability of greenhouses by integrating stable semi-transparent organic photovoltaics,” recently published in Nature Sustainability.
They built the cell with a glass and indium tin oxide (ITO) substrate, the novel interlayer, the photoactive layer, a molybdenum trioxide (MoO3) hole transport layer, and a silver (Ag) metal contact.
“The lG molecule can effectively abrogate the two main defects of the ZnO film and reduce carrier recombination at the interface,” the academics note, referring to the interlayer passivation effect. "Charge transfer from the ZnO surface to the O 2 is prevented by the lG molecule, which prevents the formation of the superoxide molecule."
According to their conclusions, the new middle layer has two different functions. On the one hand, it acts as a passivation agent and, on the other, it suppresses the formation of superoxide, which is usually triggered by the oxygen vacancy on the ZnO surface.
“Suppression of the generation of superoxide and hydroxide radicals markedly improved the operational stability of semi-transparent OPV devices encapsulated with the PM6/Y6 photoactive layer,” states the US group. “Devices with the lG interlayer retained more than 84% of their initial efficiency after 1,008 h of continuous exposure under illumination.”
With the addition of the interlayer, the cell efficiency also increased - from 11.6% to 13.5% - with an improvement in short-circuit current density from 20.5 to 22.2 mA cm-2. "In addition, due to the strong reducibility of the lG molecule, the production of radicals is reduced," the scientists say.
They also tested growing common crops such as wheat, mung beans and broccoli in a facility with a transparent glass roof with segments of inorganic solar cells and another with a roof made entirely of semi-transparent organic solar cells.
“Crops in the organic sunroof greenhouse grew more than those in a normal greenhouse,” they said, noting that the L-glutathione layer blocked ultraviolet rays, which are harmful to plant growth, as well as infrared rays, which can cause overheating of greenhouses.
“We did not expect organic solar cells to outperform a conventional glass-roof greenhouse,” says Yepin Zhao, co-author of the study. "But we repeated the experiments several times with the same results, and after further investigation and analysis, we found that the plants do not need as much sunlight to grow as we had originally thought." |
