A group of chemists from the Kaunas University of Technology in Lithuania, authors of many revolutionary innovations in the field of solar energy, have proposed another solution to increase the stability and performance of perovskite solar elements. They have synthesized a new class of carbazole-based crosslinkable materials that are resistant to various environmental effects, including the strong solvents used in solar cell production.
When applied as hole transport layers, the new materials developed in the laboratories of Kaunas University of Technology (KTU) have made it possible to achieve the 16.9% efficiency of perovskite cells at reverse architecture on the first attempt. It is expected to achieve higher efficiency during optimization.
New thermally cured materials to provide strength
Hybrid organic-inorganic perovskite solar cells have attracted worldwide attention as a competitive alternative to conventional silicon-based solar technologies. They are cheaper, more flexible and have higher power conversion efficiency. Scientists around the world are working to solve problems related to improving the stability and other characteristics of perovskite solar elements. These next-generation layered solar cells can have two architectonic structures – regular (nip) and inverted (pin) structures. In the latter, the hole-carrying materials are deposited under the perovskite absorber layer.
“While pin cells have many advantages over regular architecture perovskite solar cells, they have serious shortcomings. For example, hole-transporting compounds must be able to withstand the strong polar solvents used to form the light-absorbing perovskite layer, which is placed on top,” says Professor Vytautas Getautis, Chief Researcher at the Faculty of KTU chemical technology.
To solve this problem, in pin architectures, polymers are often used as hole transport materials. However, due to solubility issues, a polymer layer is not easy to form; moreover, it is difficult to control the recurrence of reactions and to synthesize the same structure. In an effort to solve this problem, KTU researchers created a hole transport layer of carbazole-based molecules, which was then thermally polymerized on the spot to obtain a cross-linking effect.
“The cross-linked polymer has a three-dimensional structure. It is highly resistant to various effects, including strong solvents used when forming a light-absorbing perovskite layer. We have used several groups of molecules and developed materials which, although used as a hole-transporting layer, can improve the efficiency of an inverted perovskite solar cell to almost 17%,” says PhD student Šarūnė Daškevičiūtė- Gegužienė, who synthesized these compounds. .
The invention described above was the subject of a cover article in Chemical communications, published by the Royal Society of Chemistry, UK. The cover image was created by And the unicornsa Lithuanian design company.
Creation of a tandem solar cell that breaks all records
The research group led by Professor Getautis has developed many cutting-edge inventions aimed at improving the efficiency of solar cells. Among them are synthesized compounds, which self-assemble into a thin layer of molecules that acts as a hole transport material. The silicone-perovskite solar tandem produced from said materials has achieved an efficiency of more than 29 percent. According to Professor Getautis, this latest tandem combination will soon become the commercial alternative to silicon-based solar cells – more efficient and cheaper.
“Our research area aims to improve existing technologies for perovskite solar elements and in this area, we have achieved the best results with self-assembling single-layer technology. However, science often develops in several directions, as we need to explore ways to make the best use of solar energy,” says Professor Getautis.
Although perovskite cells are a novelty compared to silicon-based solar technologies, several companies have already commercialized different products based on perovskite technology. Among them are semi-transparent flexible interior elements, portable electronic devices for controlling the population of wild animals and various architectural solutions. And that’s just the beginning.
According to Professor Getautis, of all renewable energies, solar energy has the greatest potential and is the least exploited. However, thanks to new research, this field is growing exponentially. It is estimated that by 2050, about half of the electricity used on earth will be generated from solar energy.
“Solar energy is completely green – it is non-polluting and the solar farms installed do not require much maintenance. Given the current events and the energy crisis, more and more people are interested in installing solar power plants in their homes or owning a share of a solar park. It’s an energy future”, is convinced Professor Getautis.
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