Solar energy has a clear favorite to lead the future: tandem solar cells. The idea is brilliant and simple on paper, since if you combine traditional silicon with a top layer of revolutionary perovskite, you create a “super panel.” Perovskite swallows high-energy, short-wave light, and silicon finishes the job with longer waves. So the result is capturing much more solar spectrum and generating more electricity than with traditional plates.
The valley of industrial death. The problem is that the photovoltaic industry had been banging its head against a wall for years. Perovskite was a wonder in the “Petri dish” of the laboratory, but manufacturing those very thin layers on a large scale, uniformly and quickly, was a true technical nightmare. Technology ran the risk of remaining an eternal promise, until a bridge built between Karlsruhe and Valencia showed that the problem was not the material, but the method.
The 10 minute record. A team of researchers from the Karlsruhe Institute of Technology (KIT) in Germany and the University of Valencia, supported by institutions in France and Argentina, has just published a historic milestone in the magazine Nature Energy. They have designed an ultra-fast, solvent-free vacuum process that deposits the layer of perovskite at a pace never seen before. They have managed to manufacture tandem cells with a very high efficiency of 24.3% and the conversion process lasts just 10 minutes.
To understand why this turns the industry upside down, you have to look at the factory numbers. As Professor Ulrich Paetzold (KIT) explainsIn the industry, not only efficiency matters, but also that the process is robust and scalable. This new method achieves a deposition rate of 47 nanometers per minute, that is, a speed ten times greater than that of conventional thermal evaporation methods. In addition, it consumes very little material and allows sources to be reused, drastically reducing costs.
The “magic” of sublimation. The technique is called Closed Space Sublimation (CSS). We could say that it is like a microscopic oven: the precursor materials evaporate and collide directly against the silicon cell, which is placed just a few millimeters away. There they react on site to form the structure of the perovskite almost magically. Sofía Chozas-Barrientos, researcher at the University of Valencia, emphasizes that this system It allows you to do without solvents and save a lot of time.
However, the recipe needed to be refined. For the tandem to work, the perovskite The upper part must act as a spectral filter (have a wider bandgap), and this is achieved by adding bromine. The drama was that, when trying to introduce bromine, it literally vanished during the process. The solution, according to researcher Alexander Dierckswas to create a mixed organic source by mixing methylammonium iodide and methylammonium bromide in an exact ratio of 3 to 1. Thus they managed to retain the bromine and nail an ideal band efficiency of 1.64 eV.
Ready for the real world. The point is that good solar panels are not smooth; They are full of textures (with micropyramid shapes) to better catch the light. And this CSS process has worked perfectly on smooth, nanostructured and microstructured silicon, without having to touch a single button in the machine’s settings. Microscopes confirmed impeccable coverage in all topographies.
As Professor Henk Bolink summarizesfrom the University of Valencia, a process that only works on smooth laboratory surfaces is of no use in industry. The fact that this sublimation achieves uniform layers on textured silicon is what makes this advancement real, viable and marketable.
The future, on the roofs. Closing the gap between the laboratory and the factory is the great challenge of our energy era. With this Spanish-German milestone, the mass production of tandem solar technology finally removes the “unviable” label. The perovskite revolution no longer has to wait decades; is ready to make the leap to factories and, very soon, to rooftops around the world.
Image | Eurekalert
GIPHY App Key not set. Please check settings