Researchers create new materials that could increase the stability of perovskite solar cells


The cross-linking effect provides resistance to new compounds synthesized by Lithuanian chemists. Credit: And the unicorns

A group of chemists from the Kaunas University of Technology in Lithuania, the developers of many breakthrough innovations in the field of solar energy, have come up with 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 achieved the 16.9% efficiency of inverted architecture perovskite cells 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 new 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, the hole transport compounds should be able to withstand the strong polar solvents used to form a layer of light-absorbing perovskite, which is placed on top,” says Professor Vytautas Getautis, senior researcher at the KTU Faculty of 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 in situ to achieve a crosslinking effect.

“The cross-linked polymer has a three-dimensional structure. It is very resistant to various effects, including the strong solvents used when forming a light-absorbing perovskite layer. We have used several groups of molecules and developed materials that, although used as a hole-transporting layer, can improve the efficiency of an inverted perovskite solar cell by almost 17%,” says Ph.D. student Šarūnė Daškevičiūtė-Gegužienė, who synthesized these compounds.

The invention described above was the subject of a cover article in Chemical communications.

Record-breaking tandem solar cell

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 using said materials achieved an efficiency of more than 29%. According to Professor Getautis, this latest tandem combination will soon become the more efficient and cheaper commercial alternative to silicon-based solar cells.

“Our area of ​​research aims to improve existing technologies for perovskite solar elements and in this area we have achieved the best results with self-assembly-monolayer technology. However, science is often developed in several directions, because we need to explore ways to make the best use of solar energy,” explains Professor Getautis.

Although perovskite cells are new 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 installed solar farms do not require much maintenance. In view of current events and the energy crisis, more and more people are interested in installing solar power plants at home or owning a share of a solar farm is an energy future”, is convinced Professor Getautis.

A major breakthrough for stable, high-efficiency perovskite solar cells

More information:
Sarune Dakeviciute-Geguziene et al, Cross-linkable carbazole-based hole transport materials for perovskite solar cells, Chemical Communications (2022). DOI: 10.1039/D2CC02612K

Provided by Kaunas University of Technology

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