While the global demand for renewable energy is increasing dramatically, scientists from Germany and Lithuania have developed a new solution for developing cost-effective solar technology.
Researchers from Kaunas University of Technology (KTU), Lithuania, have synthesized a novel material that self-assembles to produce an electrode layer that has a thickness of just one molecule. This study offers a facile method for achieving highly efficient perovskite single-junction and tandem solar cells. A Japanese company has purchased a license to produce the material.
Earlier, it was difficult to achieve perovskite-based solar cells, integrating high efficiency and low price. Large-scale production poses one specific challenge—the limited versatility and the high price of the available hole-selective contacts. Chemists at KTU have successfully solved this problem.
Solar element is akin to a sandwich, where all of the layers have its function, i.e. to absorb the energy, to separate the holes from electrons, etc. We are developing materials for the hole-selective contact layer, which is being formed by the molecules of the materials self-assembling on the surface of the substrate.
Artiom Magomedov, Co-Author of the Invention and PhD Student, Faculty of Chemical Technology, Kaunas University of Technology
The developed monolayers can be referred to as an ideal hole transporting material, since they are cost-effective, made by a scalable method, and also create an excellent contact with the perovskite material.
The self-assembled monolayers (SAMs) measure only 1–2 nm, spanning the entire surface; the surface is dipped into a diluted solution to deposit the molecules on it. These molecules can form SAMs on numerous oxides and are based on carbazole head groups containing phosphonic acid anchoring groups.
According to the researchers, the application of the SAMs helped in preventing the issue relating to the rough surface of the CIGS cell. A monolithic CIGSe/perovskite tandem solar cell of 23.26% efficiency was achieved by incorporating a SAM-based perovskite solar cell into a tandem design. This is presently a world record for this type of technology.
Furthermore, one of the recently developed SAMs utilized in the Si/perovskite tandem solar cell achieved an efficiency of 27.5%, which almost breaks the world record.
Perovskite-based single-junction and tandem solar cells are the future of solar energy, as they are cheaper and potentially much more efficient. The limits of efficiency of currently commercially used silicon-based solar elements are saturating. Moreover, the semiconductor-grade silicon resources are becoming scarce and it is increasingly more difficult to extract the element.
Vytautas Getautis, Professor and Research Head, Kaunas University of Technology
The amount of solar energy that reaches the Earth’s surface in one hour could be sufficient to cover the annual requirement of the electricity of all mankind, said Magomedov.
The young researcher added that, “The potential of the solar energy is immense.”
With conventional technologies, 1 g of silicon (Si) is sufficient to create only a couple of square centimeters of the solar element. But 1 g of the material produced at KTU is adequate to cover up to 1000 m2 of the surface. Additionally, the self-assembling organic material produced at KTU is considerably cheaper when compared to the substitutes presently utilized in photovoltaic elements.
A group of chemists at KTU has been analyzing the application of the self-assembling molecules in solar cells for about two years. The material synthesized at KTU was used in the production of an operating solar cell in association with the Centre for Physical Sciences and Technology (Lithuania) and Helmholtz Zentrum Berlin (HZB), Germany.
A Japanese company has bought the license to create the material produced at KTU. The material, known as MeO-2PACz and 2PACz, will soon be available at the commercial scale. This implies that novel technology utilizing self-assembling compounds can be additionally studied in the best laboratories of the globe, and this can ultimately find its way into the industry.
The paper titled “Conformal monolayer contacts with lossless interfaces for perovskite single junction and monolithic tandem solar cells” was co-authored by KTU scientists (corresponding author is Artiom Magomedov). It was published in Energy & Environmental Science on October 2nd, 2019.