Researchers have developed a technique to stabilize a promising material often called perovskite for low cost solar cells, with out compromising its near-perfect efficiency.
The researchers, from the University of Cambridge, used an natural molecule as a ‘template’ to information perovskite movies into the specified section as they type. Their outcomes are reported within the journal Science.
Perovskite supplies provide a less expensive alternative to silicon for producing optoelectronic units equivalent to solar cells and LEDs.
There are many various perovskites, ensuing from completely different mixtures of components, however some of the promising to emerge in recent times is the formamidinium (FA)-based FAPbI3 crystal.
The compound is thermally steady and its inherent ‘bandgap’ – the property most carefully linked to the vitality output of the machine—just isn’t far off ultimate for photovoltaic purposes.
For these causes, it has been the main focus of efforts to develop commercially obtainable perovskite solar cells. However, the compound can exist in two barely completely different phases, with one section resulting in glorious photovoltaic efficiency, and the opposite leading to little or no vitality output.
“A big problem with FAPbI3 is that the phase that you want is only stable at temperatures above 150 degrees Celsius,” mentioned co-author Tiarnan Doherty from Cambridge’s Cavendish Laboratory. “At room temperature, it transitions into another phase, which is really bad for photovoltaics.”
Recent options to maintain the material in its desired section at decrease temperatures have concerned including completely different constructive and adverse ions into the compound.
“That’s been successful and has led to record photovoltaic devices but there are still local power losses that occur,” mentioned Doherty. “You end up with local regions in the film that aren’t in the right phase.”
Little was recognized about why the additions of those ions improved stability general, and even what the ensuing perovskite construction regarded like.
“There was this common consensus that when people stabilize these materials, they’re an ideal cubic structure,” mentioned Doherty. “But what we’ve shown is that by adding all these other things, they’re not cubic at all, they’re very slightly distorted. There’s a very subtle structural distortion that gives some inherent stability at room temperature.”
The distortion is so minor that it had beforehand gone undetected, till Doherty and colleagues used delicate structural measurement methods that haven’t been extensively used on perovskite supplies.
“Once we figured out that it was the slight structural distortion giving this stability, we looked for ways to achieve this in the film preparation without adding any other elements into the mix.”
Co-author Satyawan Nagane used an natural molecule known as Ethylenediaminetetraacetic acid (EDTA) as an additive within the perovskite precursor answer, which acts as a templating agent, guiding the perovskite into the specified section because it kinds. The EDTA binds to the FAPbI3 floor to offer a structure-directing impact, however doesn’t incorporate into the FAPbI3 construction itself.
“With this method, we can achieve that desired band gap because we’re not adding anything extra into the material, it’s just a template to guide the formation of a film with the distorted structure—and the resulting film is extremely stable,” mentioned Nagane.
“In this way, you can create this slightly distorted structure in just the pristine FAPbI3 compound, without modifying the other electronic properties of what is essentially a near-perfect compound for perovskite photovoltaics,” mentioned co-author Dominik Kubicki from the Cavendish Laboratory, who’s now primarily based on the University of Warwick.
The researchers hope this elementary examine will assist enhance perovskite stability and efficiency. Their personal future work will contain integrating this approach into prototype units to discover how this system might assist them obtain the right perovskite photovoltaic cells.
“These findings change our optimisation strategy and manufacturing guidelines for these materials,” mentioned senior creator Dr. Sam Stranks from Cambridge’s Department of Chemical Engineering & Biotechnology. “Even small pockets that aren’t slightly distorted will lead to performance losses, and so manufacturing lines will need to have very precise control of how and where the different components and ‘distorting’ additives are deposited. This will ensure the small distortion is uniform everywhere—with no exceptions.”
Tiarnan A. S. Doherty et al, Stabilized tilted-octahedra halide perovskites inhibit native formation of performance-limiting phases, Science (2021). DOI: 10.1126/science.abl4890. www.science.org/doi/10.1126/science.abl4890
University of Cambridge
Templating approach stabilises ‘ultimate’ material for alternative solar cells (2021, December 23)
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