Lead-free - Page 4

An international researchers team recently found that a new 'double perovskite' material could become a more environmentally friendly platform for spintronics devices thanks to its lead-free nature. While the material in its current form is only magnetic below 30 K ' too low for practical applications ' developers at Linköping University in Sweden, together with colleagues in the US, the Czech Republic, Japan, Australia and China, say that their preliminary experiments are a promising step towards making rapid and energy-efficient information storage devices from this novel optoelectronic material.

Recently, researchers discovered that lead halide perovskites display interesting spin properties thanks to lead's strong spin-orbit coupling. This coupling links the motion of an electron to its quantum spin, and its strength determines how much the intrinsic spin of an electron will interact with the magnetic field induced as the electron moves through the material. Such a coupling is therefore important not only for the magnetic properties of a material, but also for the performance of any spintronics devices.

Scientists from the South Dakota School of Mines and Technology and Michigan State, Toledo and Wisconsin universities have found bifacial perovskite PV cells have the potential to become more environmentally friendly than conventional crystalline silicon devices, due to their increased energy yield.

The scientists examined sites at Toledo, in Ohio and Golden, Colorado, to take account of high and low latitude and humidity conditions. The researchers analyzed the environmental impact of single-junction, bifacial perovskite cells with high and low bandgaps, and multi-junction devices of the same type with two-terminal (2T) and four-terminal (4T) structures. They quantified the life cycle energy production from the cells under real-world conditions and benefiting from diverse albedo environments including installation above sandstone, concrete, grass and snow.

Scientists from the Korea Institute of Machinery and Materials, Kyungpook National University, Sungkyunkwan University, Sejong University and Yonsei University in Korea, in collaboration with Uppsala University in Sweden, Imperial College London and National Renewable Energy Laboratory in the U.S, recently devised a way to sustainably collect pollutants secreted from PSCs without sacrificing the panel itself. Using this new approach, the scientists were able to safely recycle 99.7% of lead in their samples.

In the study describing their work, the researchers explain that they're not the first to attempt to tackle this issue, but that previous approaches to adsorbing lead have been limited by the number of naturally occurring lead solvents.

An international collaboration led by Antonio Abate, HZB, and Zhao-Kui Wang, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, China, has achieved a breakthrough that opens up a path to non-toxic perovskite-based solar cells that provides stable performance over a long period.

They use tin instead of lead but have created a two-dimensional structure by inserting organic groups within the material, which leads to so-called 2D Ruddlesden-Popper phases.

University of Groningen scientists are investigating in situ how lead-free perovskite crystals form and how the crystal structure affects the functioning of the solar cells, as part of their quest to find alternatives to lead-based perovskites.

The best results in solar cells have been obtained using perovskites with lead as the central cation. As this metal is toxic, tin-based alternatives have been developed, for example, formamidinium tin iodide (FASnI₃). This is a promising material; however, it lacks the stability of some of the lead-based materials. Attempts have been made to mix the 3D FASnI₃ crystals with layered materials, containing the organic cation phenylethylammonium (PEA). "My colleague, Professor Maria Loi, and her research team showed that adding a small amount of this PEA produces a more stable and efficient material," says Assistant Professor Giuseppe Portale.

Researchers at the Pohang University of Science & Technology (POSTECH) have developed eco-friendly-solvent processable hole transport polymers by using peppermint oil and walnut aroma food additives and the polymer can prevent lead leakage.

The POSTECH research team consisted of Prof. Taiho Park and Junwoo Lee, that developed Alkoxy-PTEG - hole transport polymers that could be dissolved in peppermint oil, by applying ethylene glycol side chains when producing perovskite solar cells. Also, the team confirmed that this polymer captured leaking lead in aging perovskite solar cells.

Researchers at Northern Illinois University and the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) in Colorado have reported on a potential breakthrough in the development of hybrid perovskite solar cells.

Led by Tao Xu of NIU and Kai Zhu of NREL, the scientists have developed a technique to sequester the lead used to make perovskite solar cells and minimize potential toxic leakage by applying lead-absorbing films to the front and back of the solar cell.

Researchers led by Prof. Antonio Abate at the Helmholtz-Zentrum Berlin have designed a study to investigate lead hazards relating to perovskite soar cells. They cooperated with plant scientists from the Fujian Agriculture and Forestry University, China, where the experiments were carried out, and with a group from the university of Naples, Italy.

Mint plants grown on control soil (left) and perovskite-contaminated soil (right). Credit: Nature

The plant experts prepared contaminated soil samples with different concentrations of lead from either perovskite solar cells or other lead sources and cultivated different plants. After a growth period, they analyzed the lead content in leaves and other parts of the plant. They found that lead from perovskite solar cells is 10 times more bioavailable than lead from other industrial sources.

Chinese manufacturer GCL recently indicated that it is nearing commercialization of perovskite solar technology. 'Once the conversion rate [of] perovskite is close to what monocrystalline product does, which is coming soon, the only obstacle for perovskite to take [the] place of mono is the limitation of its production capacity,' GCL Nano Technology general manager Fan Bin said at a recent industry conference which considered the potential of perovskite.

Discussing GCL's work with perovskites, Fan said his company's lab has achieved a conversion efficiency of 16% on a large panel and he is confident 18% could be achieved by the end of the year. With a theoretical conversion limit of around 33% thought to apply to perovskite cell efficiency ' and possibly up to 47% for a tandem device ' the manager voiced confidence perovskites would soon surpass the 18% threshold.

Researchers from the University of Surrey's Advanced Technology Institute (ATI) have produced a perovskite solar cell which contains 50% less lead, replaced with the more innocuous tin. By fine-tuning their tin solar cell, the researchers were able to create a product that is able to absorb infrared light in a similar manner as silicon cells. They also found that by stacking lead-only cells with the ones mixed with tin can lead to power conversion results that outperform those of silicon-only power cells.

Indrachapa Bandara, lead author of the study and PhD student at ATI, said: 'We are starting to see that many countries are treating the threat of climate change with the seriousness it deserves. If we are to get a handle on the problem and put the health of our planet on the right track, we need high-performing renewable energy solutions.... Our study has shown that tin based perovskite solar cells have an incredible amount of potential and could help countries such as the United Kingdom reach its target of becoming carbon neutral by 2050'.