Perovskite, a mineral from the group of oxides, can be used as an option for the construction of photovoltaic panels with almost perfect performance, according to researchers.
This raw material is a cheaper alternative to silicon to produce optoelectronic devices such as solar cells and LEDs.
An affordable alternative to creating solar panels
Researchers from the University of Cambridge reported, through a publication in the journal Science, an investigation in which they used an organic molecule as a “template” to guide perovskite films in the desired phase as they are formed.
There are many different perovskites, resulting from different combinations of elements. The research focused on the use of formamidinium, which gives rise to a compound that is thermally stable and is not far from being suitable for photovoltaic applications.
For these reasons, efforts have arisen to develop perovskite solar cells for commercial distribution. However, the compound can exist in two slightly different phases, with one phase leading to excellent photovoltaic performance, and the other resulting in very little energy production.
“A big problem with FAPbI3 – the compound mentioned above – is that the desired phase is only stable at temperatures above 150 degrees Celsius”, commented Tiarnan Doherty, a co-author of the study and a fellow at the Cambridge Cavendish Laboratory. “At room temperature, it goes into another phase, which is really bad for photovoltaic energy”added.
Recent solutions to keep the material in its desired phase at lower temperatures have involved the addition of different positive and negative ions to the compound. “That has been successful and has led to record PV devices, but there are still local power losses occurring”Doherty noted.
About that process, little was known about why the additions of these ions improved overall stability. Furthermore, neither the structure of the resulting perovskite was known. “There was a common consensus that when people stabilize these materials, they are an ideal cubic structure”said Doherty. “But what we have shown is that by adding all these other things, they are not cubic at all, they are very slightly distorted. There is a very subtle structural distortion that gives some inherent stability at room temperature »he commented.
The distortion is so small that it had previously gone undetected, until Doherty and his colleagues employed sensitive structural measurement techniques, previously not widely used with perovskite materials. Specifically, scanning electron diffraction, nano-X-ray diffraction and nuclear magnetic resonance were used to see, for the first time, what this stable phase really looked like.
“Once we discovered that it was the slight structural distortion that gave this stability, we looked for ways to achieve this in film preparation without adding anything else to the mix.”.
Research co-author Satyawan Nagane used an organic molecule called ethylenediaminetetraacetic acid (EDTA) as an additive in the perovskite precursor solution, acting as a templating agent that guides the perovskite to the desired phase as it forms. . EDTA connects to the mineral surface, to give a structure-directing effect, without being directly incorporated into it.
“With this method, we can achieve that desired band gap because we are not adding anything extra to the material, it is just a template to guide the formation of a film with the distorted structure, and the resulting film is extremely stable.”Nagane said.
“These findings change our optimization strategy and manufacturing guidelines for these materials”said the study’s lead author, Dr Sam Stranks, from Cambridge’s Department of Chemical Engineering and Biotechnology. “Even small pockets that are not slightly distorted will lead to performance losses, so manufacturing lines will need to have very precise control of how and where different ‘distorting’ components and additives are deposited. This will ensure that the small distortion is uniform throughout, with no exceptions ».
The researchers hope that this study will help improve the stability and performance of perovskite. Your next research steps will focus on integrating this approach into prototype devices, to explore how this technique can help you get the perfect perovskite PV cells.