Improved polymer additive enhances perovskite solar cells

by Simon Mansfield

Sydney, Australia (SPX) May 16, 2024

Perovskite solar cells, known for their lightweight and flexible nature, are inexpensive and easy to manufacture. They are seen as a promising technology that can be attached to various surfaces. However, these solar cells currently lack durability and efficiency. New research highlights how adding a polymerized ionic liquid to the metal halide perovskite material can improve their performance, potentially facilitating wider adoption of perovskite solar cells.

“The commonly employed solution processing method for fabricating perovskite layers introduces many defects in both the bulk and surface of the perovskite layer. These intrinsic defects within the perovskite absorption layer pose a significant constraint on the overall performance of the devices. Additive engineering has been demonstrated to be effective as a strategy for defect passivation and performance enhancement in perovskite solar cells,” said Qi Cao, a researcher at Northwestern Polytechnical University in Xi’an, China.

Researchers are enhancing the properties of ionic liquids by creating polymerized versions. In this study, they synthesized a poly ionic liquid called poly4-styrenesulfonyl(trifluoremethylsulfonyl)imidepyridine (PSTSIPPyri).

The addition of PSTSIPPyri to the perovskite solar cell helps prevent halide ion migration, maintains the crystal structure, and improves the solar cell’s stability by fixing organic and halide ions.

“To date, researchers have devoted considerable attention to the meticulous selection of additives that enhance the performance of perovskite solar cells. Among these, ionic liquids have received widespread attention. Ionic bonds in ionic liquids tend to be stronger and more stable, and they offer various tunable properties, including viscosity, polarity, and conductivity,” said Xuanhua Li, a researcher at Northwestern Polytechnical University. “This tunability makes it possible to fine-tune the ionic liquid properties to meet the specific requirements of the perovskite film, thereby optimizing device performance.”

Testing of the PSTSIPPyri additive involved aging perovskite films for 300 hours at 85C and 60% relative humidity. The enhanced perovskite film showed a slower rate of change than the control film. It also retained 84.5% of its efficiency after 1000 hours in a high humidity, high heat environment, compared to 43.6% for the control.

Long-term durability tests showed that with PSTSIPPyri, the perovskite solar cell maintained 87.6% of its power conversion efficiency after 1,500 hours of continuous light, while the control only maintained 61.1%.

“Incorporating PSTSIPPyri as an additive leads to a significant enhancement in the power conversion efficiency of inverted perovskite solar cells from 22.06% to 24.62%. They also demonstrate excellent long-term operational stability,” said Cao. “This strategy illustrates the potential of poly ionic liquids as a promising additive for perovskite solar cells, offering both high performance and stability.”

Other contributors include Xingyuan Chen, Tong Wang, Jiabao Yang, Xingyu Pu, Hui Chen, Bingxiu Xue, and Jianbo Yin at Northwestern Polytechnical University in Xi’an, China; Long Jiang at the CNPC Tubular Goods Research Institute in Xi’an, China.

Research Report:Efficiency enhancement to 24.62% in inverted perovskite solar cells through poly (ionic liquid) bulk modification

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Solar power heats materials over 1,000 degrees Celsius

by Robert Schreiber

Berlin, Germany (SPX) May 16, 2024

Researchers at ETH Zurich have developed a method to generate heat exceeding 1,000 degrees Celsius using solar power. This innovation could replace fossil fuels in energy-intensive industries like steel and cement production. The study, published in the journal Device on May 15, utilizes synthetic quartz to capture solar energy, demonstrating the potential for clean energy in these industries.

“To tackle climate change, we need to decarbonize energy in general,” said Emiliano Casati of ETH Zurich. “People tend to only think about electricity as energy, but in fact, about half of the energy is used in the form of heat.”

The production of glass, steel, cement, and ceramics requires high temperatures, traditionally achieved by burning fossil fuels. These industries account for about 25% of global energy consumption. Researchers have explored using solar receivers to concentrate and build heat, but transferring solar energy efficiently above 1,000 degrees Celsius has been challenging.

Casati’s team enhanced solar receivers using quartz, which traps sunlight through the thermal-trap effect. They created a device with a synthetic quartz rod and an opaque silicon disk to absorb energy. When exposed to intense sunlight, the device’s absorber plate reached 1,050 degrees Celsius, while the quartz rod’s other end remained at 600 degrees Celsius.

“Previous research has only managed to demonstrate the thermal-trap effect up to 170 degrees Celsius,” Casati said. “Our research showed that solar thermal trapping works not just at low temperatures, but well above 1,000 degrees Celsius. This is crucial to show its potential for real-world industrial applications.”

Using a heat transfer model, the team simulated the quartz’s efficiency under various conditions. The model showed that thermal trapping achieves target temperatures at lower concentrations with similar performance or higher efficiency at equal concentrations. For example, a state-of-the-art receiver has an efficiency of 40% at 1,200 degrees Celsius with a concentration of 500 suns. A receiver shielded with 300 mm of quartz achieves 70% efficiency at the same temperature and concentration. The unshielded receiver requires at least 1,000 suns for comparable performance.

Casati’s team is optimizing the thermal-trapping effect and exploring new applications. They have tested other materials, such as different fluids and gases, to reach even higher temperatures. The ability of these semitransparent materials to absorb light or radiation is not limited to solar radiation.

“Energy issue is a cornerstone to the survival of our society,” Casati said. “Solar energy is readily available, and the technology is already here. To really motivate industry adoption, we need to demonstrate the economic viability and advantages of this technology at scale.”

Research Report:Solar thermal trapping at 1000C and above

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Lithuanian researchers advance solar cell technology

by Robert Schreiber

Berlin, Germany (SPX) May 16, 2024

Researchers from Kaunas University of Technology (KTU), Lithuania, who previously developed high-efficiency solar cells, have expanded their invention. The self-assembled monolayers can now be applied in both inverted and regular structure perovskite solar cells.

Self-assembling molecules form a single-molecule-thick layer, acting as an electron-transporting layer in solar cells.

“The molecules that make up these monolayers, like a clever glue, coat the surface of the constructed devices with a thin one molecule thick layer. And this is not random, they don’t stick wherever they go, but attach themselves by chemical bonds only where they are in contact with conductive metal oxide,” explained Tadas Malinauskas, Professor at KTU’s Faculty of Chemical Technology and one of the inventors of the new technology.

According to Malinauskas, creating such a layer is a simple and material-efficient process that requires a glass substrate with an electrically conductive metal oxide layer to be immersed in or sprayed with a highly diluted solution of the compound. The self-assembling molecules attach only to the metal oxide surface, with non-adhering molecules being washed away. This creates a thin layer precisely where it is needed.

KTU researchers have been synthesizing and studying charge-transporting organic materials for several years, focusing previously on molecules for positive charge transfer in perovskite solar cells.

“We can already say with confidence that these molecules have given a major boost to the development of the next generation solar cells. So, our next step is quite logical: to develop analogous molecules that can carry negative charges, and to apply these materials in perovskite solar cells,” said Vytautas Getautis, professor at the KTU Faculty of Chemical Technology and head of the research group.

Although it is a very thin layer, its role in solar cells is critical. Malinauskas compared its function to that of an automatic gate in the subway, allowing only one type of charge to pass through towards the electrode, thereby increasing solar cell efficiency.

Perovskite solar cell structures vary in layer sequence. In the regular structure, a negative charge transporting layer is formed on a transparent substrate, followed by light-absorbing and positive charge transporting layers. In the inverted structure, the positive and negative charge transport layers are swapped.

KTU PhD student Lauryna Monika Svirskaite explained that the main difference between the two structures lies in their application areas. The regular structure is used for studying low-cost, easier-manufactured but less efficient solar cells, while the inverted architecture allows for more efficient combined devices, known as tandem devices.

Currently, as both structures are being intensively researched, KTU scientists believe that their new invention is as significant and promising as their previous developments.

The new invention resulted from collaboration with scientists from King Abdullah University of Science and Technology (KAUST).

“We, KTU chemists, were responsible for the development, improvement, and optimisation of the materials and coating technology, while our colleagues from Saudi Arabia investigated the performance of it in solar cells,” revealed Malinauskas.

Greta Zekiene, head of Intellectual Property Management at KTU’s National Innovation and Entrepreneurship Centre (NIEC), said the demand for this invention is surprisingly high. Interest in the invention’s industrial use preceded the patent application filing.

“A Japanese company, with whom we already have several licences for inventions in this field, immediately expressed the interest to have the innovation in their product portfolio. They were waiting for us to prepare a patent application. The process of negotiating a licence agreement started right away,” said Zekiene.

She emphasized that obtaining a patent is not necessary for commercializing an invention, as it depends on the individual case. Commercialization can occur at any time if a business declares its intention to license or take over all the property rights.

Zekiene added that inventions in the field of solar cells made by the Synthesis of Organic Semiconductors research group are the strongest in KTU’s patent portfolio and receive significant interest from businesses. “We feel proud and acknowledged when companies want to start using the inventions as soon as possible,” she said.

Research Report:Nonfullerene Self-Assembled Monolayers As Electron-Selective Contacts for n-i-p Perovskite Solar Cells

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