Stability - Page 12

Researchers at Nanjing University, Nankai University, East China Normal University and University of Toronto have developed new inorganic wide-bandgap perovskite subcells that could increase the efficiency and stability of all-perovskite tandem solar cells. Their design involves the insertion of a passivating dipole layer at the interface between organic transport layers and inorganic perovskites within the cells.

The scientists explained that efficient tandem solar cells made using hybrid organic inorganic wide-bandgap perovskites have thus far maintained only 90% of their initial PCE for 600 hours of operation at their maximum power point (MPP). Therefore, achieving long-term stability has become a critical issue for the commercialization of all-perovskite tandem solar cells.

Researchers at the Indian Institute of Technology Bombay have reported NIR-transparent perovskite solar cells (PSCs) with the stable triple cation perovskite as the photo-absorber and subsequent integration with a Si solar cell in a 4T tandem device. The scientists said that the cell provides outstanding stability in the dark, as well as continuous heating conditions.

The top perovskite cell incorporates a room-temperature sputtered transparent conducting electrode (TCE) as a rear electrode. It has an n–i–p structure and utilizes an anti-reflecting coating, an electron transport layer (ETL) made of tin(IV) oxide (SnO₂), a perovskite layer, a molybdenum oxide (MoOx) layer, and a spiro-OMeTAD hole transport layer (HTL). The MoOx buffer layer protects the perovskite photo-absorber and charge transport layers from any sputter damage.

Researchers from the University of Surrey, University of Toronto, University of Stuttgart and Ulsan National Institute of Science and Technology have found that stabilizing the perovskite "photoactive phases" – the specific part of the material that is responsible for converting light energy into electrical energy – is the key step towards extending the lifespan of perovskite solar cells. The stability of the photoactive phase is important because if it degrades or breaks down over time, the solar cell will not be able to generate electricity efficiently. Therefore, stabilizing the photoactive phase is a critical step in improving the longevity and effectiveness of perovskite solar cells.

In the study, the team assessed the current understanding of these phase instabilities and summarized the approaches for stabilizing the desired phases, covering aspects from fundamental research to device engineering. The scientists subsequently analyzed the remaining challenges for perovskite PVs and demonstrated the opportunities to enhance phase stability with ongoing materials discovery and in operando analysis. Finally, the team proposed future directions towards upscaling perovskite modules, multijunction PVs and other potential applications.

An international research team that includes scientists from EPFL in Switzerland, Middle East Technical University (METU) in Turkey, Lomonosov Moscow State University in Russia and The University of Tokyo has fabricated a quasi-2D perovskite solar cell with a unique type of salt to enhance hole extraction. 

The triple-cation perovskite absorber was treated with phenethylammonium iodide (PEAI), a modulator that alters the perovskite film's surface energy and forms a quasi-2D structure without further annealing. The result is a 23.08%-efficient device that is also able to retain 95% of its initial efficiency after 900 hours.

Researchers at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), University of Macau and Celanese (China) Holding have developed a long-alkyl- chain anionic surfactant (LAS) additive that can significantly improve the long-term operational stability of perovskite/silicon tandem solar cells.

Traditional methods to improve the stability of perovskite solar cells include encapsulation, crystallization engineering, and defect passivation. Similar to “stress corrosion” in metals, glass and polymers, subcritical perovskite deterioration inevitably occurs due to tensile stress during the fabrication and operation, which degrades device performance. To suppress the “stress corrosion”, the researchers developed the novel LAS additive for the perovskite/silicon tandem solar cells.

Researchers at the University of California, Davis College of Engineering and Georgia Institute of Technology are using machine learning to identify new materials for high-efficiency solar cells. Using high-throughput experiments and machine learning-based algorithms, they have found it is possible to forecast the materials’ dynamic behavior with very high accuracy, without the need to perform as many experiments.

A primary challenge in the field of perovskite-based solar cells is that the perovskite devices tend to degrade faster than silicon when exposed to moisture, oxygen, light, heat, and voltage. The challenge is to find which perovskites combine high-efficiency performance with resilience to environmental conditions. Marina Leite, associate professor of materials science and engineering at UC Davis and senior author of the paper, said that “the number of possible chemical combinations alone is enormous". Furthermore, they need to be assessed against multiple environmental conditions, alone and in combination, which results in a hyperparameter space that cannot be explored using conventional trial-and-error methods. “The chemical parameter space is enormous,” Leite said. “To test them all would be very time consuming and tedious.”

The US Department of Energy (DoE) has announced USD$52 million (EUR 47.5 million) in funding for 19 research, development and demonstration projects that seek to strengthen domestic solar manufacturing, support the recycling of solar panels and develop new solar technologies.

This funding will back several projects, among which two projects, led by the Massachusetts Institute of Technology (MIT) and the University of Colorado Boulder, will receive a total of USD$18 million through the PV Research and Development funding programme to advance perovskite solar cell devices.

Perovskite solar films developed by a graduate student in the Department of Physics at UC Merced while on an internship at NASA Glenn Research Center (GRC) not only survived 10 months in space with minimal degradation, but the little damage they did incur was more than 90% reversible. 

The research team, that included scientists from UC Merced and Universities Space Research Association (National Aeronautics and Space Administration), National Renewable Energy Laboratory (NREL) and Wilberforce University, have published the results of the first long-term study of perovskite solar samples in space.

A research team, led by Prof. GUO Xin and Prof. LI Can from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), has unveiled the origin of the stability of Dion–Jacobson (DJ) phase two-dimensional (2D) perovskite materials.

Compared to traditional 3D perovskites with intrinsically low stability, 2D perovskites including the Ruddlesden–Popper (RP) phase and DJ phase are considered attractive due to their enhanced stability, especially DJ 2D perovskites based on organic diammonium cations and inorganic lead iodide octahedra, which have higher structural stability than RP ones. However, some of DJ 2D perovskites are not robust and degrade even more easily than their RP 2D counterparts, which has led to a debate over their stability. These contradictory research results have impelled scientists to search for better understanding regarding the stability mechanism of DJ 2D perovskites with different diammonium cations.

Scientists from Turkey's Konya Technical University have shown that sepiolite, a naturally occurring clay substance, can be added to perovskite precursor materials, and form a scaffold layer that can improve the efficiency and stability of solar cells. The scientists believe that this substance could be valuable in developing reproducible processes for the production of large-area perovskite solar cells.

SEM image of aerosol coated sepiolite films on FTO glasses obtained from 1 mg/ml dispersion in water. (a) 30KX and (b) 50KX magnification. Image from study

The team found that sepiolite, a naturally occurring clay mineral largely composed of silicon, magnesium and oxygen, has a very high active surface area and can easily be dispersed in solvents. It can be used without any alterations as a scaffold layer in a perovskite solar cell. The group worked with planar perovskite solar cells with an initial maximum efficiency of 7.92%, and found that cells fabricated with the sepiolite additive jumped to a maximum efficiency just over 16%, more than a 50% increase for cells produced under otherwise identical conditions.