Solar cells: breakthrough in perovskite cells brings them closer to mass use
Rice University engineers have shown that the production of highly efficient solar cells with 2D and 3D perovskite layers can be simplified by solvents that allow solution deposition of one layer without destroying the other. The work solved a long-standing conundrum in making stable and efficient solar panels with halide perovskites. The effort was to find the right solvent design to apply a 2D top layer of the desired composition and thickness without destroying the bottom 3D layer (or vice versa). A cell of this type would transform sunlight into electricity to a greater extent than either layer alone, with better stability.
Chemical and biomolecular engineer Aditya Mohite and his laboratory at Rice's George R. Brown School of Engineering reported success in building thin 3D / 2D solar cells that offer 24.5 power conversion efficiency in Science. %.
This is about as efficient as most commercially available solar cells, Mohite said.
Mohite noted: "This is really great for flexible, double-sided cells where light enters from both sides and also for rear contact cells." The 2D perovskites absorb the blue and visible photons, while the 3D side absorbs the near infrared ”. The new advance largely removes the last major obstacle to commercial production, he added.
Perovskites are cubic lattice crystals known to be efficient light harriers, but the materials tend to be stressed by light, moisture and heat. Mohite and many others have worked for years to make perovskite solar cells practical.
Mohite explained: “This is a significant achievement on several levels. One is that it is fundamentally difficult to make a solution-processed bilayer when both layers are of the same material. The problem is that they both dissolve in the same solvents. When you put a 2D layer on top of a 3D layer, the solvent destroys the underlying layer. Our new method solves this problem ”.
Mohite explained that 2D perovskite cells are stable, but less efficient at converting sunlight. 3D perovskites are more efficient but less stable. Their combination incorporates the best features of both. “This leads to very high efficiencies because now, for the first time in the field, we are able to create layers with enormous control. This allows us to control the flow of charge and energy not only for solar cells, but also for optoelectronic devices and LEDs ”.
The efficiency of test cells exposed to the laboratory equivalent of 100% sunlight for over 2,000 hours “does not degrade by even 1%”. Not counting the glass substrate, the cells were about 1 micron thick.
Solution machining is widely used in industry and incorporates a number of techniques – spin coating, dip coating, blade coating, slot die coating and others – to deposit material onto a surface in a liquid. As the liquid evaporates, the pure coating remains.
The key is the balance between two properties of the solvent itself: its dielectric constant and Gutmann's donor number. The dielectric constant is the ratio between the electrical permeability of the material and its free space. Determines the ability of a solvent to dissolve an ionic compound. The number of donors is a measure of the electron donation capacity of the solvent molecules.
"If you find the correlation between them, it turns out that there are about four solvents that allow you to dissolve the perovskites and coat them without destroying the 3D layer," said Mohite.
Their discovery should be compatible with roll-to-roll production, which typically produces 30 meters of solar cells per minute, significantly reducing production costs, still an essential element in the development of the use of solar energy.
Co-author Jacky Even, professor of physics at the National Institute of Science and Technology in Rennes, France, said, This discovery is leading, for the first time, to heterostructures of perovskite devices containing more than one active layer. The dream of designing complex semiconductor architectures with perovskites is about to come true. The next steps will be new applications and the exploration of new physical phenomena ”.
Having rolls of perovskite cells means having an efficient and low-cost photovoltaic material that can be used on a large scale.
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The article Solar cells: breakthrough in perovskite cells brings them closer to mass use comes from ScenariEconomici.it .
This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/celle-solari-passo-avanti-nelle-celle-a-perovskiti-ne-fa-avvicinare-luso-di-massa/ on Thu, 29 Sep 2022 20:23:12 +0000.