Do you know the benefits of perovskite? It is the main candidate to eventually replace silicon in the manufacture of photovoltaic cells, as it promises to be a more efficient and cheaper alternative. In fact, it already achieves an efficiency of 25,2% in the conversion of light energy into electrical energy, suring the percentage of crystalline silicon cells.
According to Ana Flávia Nogueira, a researcher at CINE (Center for Innovation in New Energies), the material has been ing stability tests and is expected to be commercialized in the coming years. Therefore, there is no doubt that perovskites, which are still in the research phase, will be able to gain more and more traction in the photovoltaic market, after all, they offer countless advantages for those who use them.
According to Jason Yoo, a researcher at MIT (Massachusetts Institute of Technology), there are a vast number of possible chemical combinations that are attracting worldwide interest. “This is partly due to the much simpler processing and manufacturing processes, which for silicon or gallium arsenide require sustained heat of over 1.000 °C. In contrast, perovskites can be processed at less than 200 °C, in solution or by vapor deposition,” he explained.
The other big advantage of this material over many other candidate replacements is that it forms extremely thin layers while still efficiently capturing solar PV energy. “Perovskite cells have the potential to be orders of magnitude lighter than silicon,” said chemist Moungi Bawendi, who is also a professor at MIT.
Yoo also pointed out that they have a wider bandgap than silicon, meaning they absorb a different part of the light spectrum and can thus complement such cells to provide even higher combined efficiencies. “What we are demonstrating is that even with a single active layer, we can achieve efficiencies that are threatening to silicon and hopefully in the range of gallium arsenide. And both of these technologies have been around much longer than perovskites,” he said.
More advantages
Another key to improving the material's efficiency, for Bawendi, is in the electron transport layer. “The perovskite itself is coated in a transparent conductive layer, used to transport an electrical current from the cell to the location where it can be used.”
“However, if it is directly attached to the perovskite itself, the electrons and their counterparts, called holes, simply recombine in place and no current flows,” he pointed out.
In the researchers’ design, the perovskite and the conductive coating are separated by an improved type of interlayer that can let electrons through, preventing recombination. The method they use is called chemical bath deposition. “It’s like slow cooking in a slow cooker,” Moungi Bawendi said.
According to the study, in a bath at 90 °C, the chemical precursors slowly decompose to form the tin dioxide layer on site. “The team realized that if we understood the decomposition mechanisms of these precursors, we would have a better understanding of how these films form. We were able to find the right window in which the electron transport layer with ideal properties can be synthesized,” he concluded.
About perovskite
Perovskite is a crystalline structure that occurs in metamorphic rocks, which are formed by changes in pre-existing rocks, caused by increased pressure and temperature. The mineral was discovered in the Ural Mountains, in Russia, by Gustav Rose, a German mineralogist, in 1939. A perovskite can be purely inorganic or hybrid, where some components are organic, as is the case of those used in solar cells.
