![]() ![]() While perovskites continue to show great promise, and several companies are already gearing up to begin some commercial production, durability remains the biggest obstacle they face. This new approach could lead to a much faster development of new alternatives, says Buonassisi, who was a co-author of that research. Searching for promising new candidate compositions for perovskites is a bit like looking for a needle in a haystack, but recently researchers have come up with a machine-learning system that can greatly streamline this process. Unlike silicon, which requires extremely high purity to function well in electronic devices, perovskites can function well even with numerous imperfections and impurities. One of the great advantages perovskites offer is their great tolerance of defects in the structure, he says. Buonassisi notes, however, that “consistently over time, the lead-based devices continue to improve in their performance, and none of the other compositions got close in terms of electronic performance.” Work continues on exploring alternatives, but for now none can compete with the lead halide versions. ![]() Many teams have also focused on variations that eliminate the use of lead, to avoid its environmental impact. Within that category, there is still a legion of possibilities, and labs around the world are racing through the tedious work of trying to find the variations that show the best performance in efficiency, cost, and durability - which has so far been the most challenging of the three. But a main focus of research activity for more than a decade has been on lead halide perovskites, according to Buonassisi says. Within the overall category of perovskites, there are a number of types, including metal oxide perovskites, which have found applications in catalysis and in energy storage and conversion, such as in fuel cells and metal-air batteries. The A and B ions are typically of quite different sizes, with the A being larger. That structure of interlaced lattices consists of ions or charged molecules, two of them (A and B) positively charged and the other one (X) negatively charged. “Perovskites are highly tunable, like a build-your-own-adventure type of crystal structure,” he says. Eventually you might cause the 3D crystal to separate into a 2D layered structure, or lose ordered structure entirely,” says Tonio Buonassisi, professor of mechanical engineering at MIT and director of the Photovoltaics Research Laboratory. For instance, if you try to stuff a molecule that’s too big into the structure, you’ll distort it. “You can mix and match atoms and molecules into the structure, with some limits. (Some researchers even bend the rules a little by naming other crystal structures with similar elements “perovskites,” although this is frowned upon by crystallographers.) The family of perovskites consists of the many possible combinations of elements or molecules that can occupy each of the three components and form a structure similar to that of the original perovskite itself. It has a three-part structure, whose components have come to be labeled A, B and X, in which lattices of the different components are interlaced. The original mineral perovskite, which is calcium titanium oxide (CaTiO 3), has a distinctive crystal configuration. The perovskite family of solar materials is named for its structural similarity to a mineral called perovskite, which was discovered in 1839 and named after Russian mineralogist L.A. The term perovskite refers not to a specific material, like silicon or cadmium telluride, other leading contenders in the photovoltaic realm, but to a whole family of compounds. They’re the subject of increasing research and investment, but companies looking to harness their potential do have to address some remaining hurdles before perovskite-based solar cells can be commercially competitive. These materials would also be lightweight, cheap to produce, and as efficient as today’s leading photovoltaic materials, which are mainly silicon. Perovskites hold promise for creating solar panels that could be easily deposited onto most surfaces, including flexible and textured ones. ![]()
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