Perovskite Solar - Page 45

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 East China University of Science and Technology, Jilin University, Huazhong University of Science and Technology, ShanghaiTech University, Chinese Academy of Sciences, Shanghai Jiao Tong University and University of Potsdam have found that a new molecular hole-transporter can improve the performance of inverted perovskite solar cells and mini modules.

Left: mini module. Upper right: contact angle of the perovskite solution on the self assembled monolayer. Lower right: PL emission of a perovskite film. Image from University of Potsdam website.

Inverted perovskite solar cells are seen as particularly promising thanks to their simple fabrication at low costs and their relative stability. Inverted perovskite solar cells resemble organic solar cells, with a layer of perovskite replacing the organic absorber layer. In the recent study, the authors developed a novel hole transport layer based on a self-assembled monolayer. This monolayer consists of amphiphilic molecules, molecules that are both hydrophilic (water-soluble) and hydrophobic (water-fearing). 

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.

U.S-based PV company, Ascent Solar Technologies (ASTI), has announced that it has entered into a USD $5 million debt financing agreement with BD1 Investment Holdings, a substantial existing stockholder of the Company. The Company will receive the monies in four monthly installments. The first tranche (for $2 million) will close in mid-May 2023. Three subsequent tranches (each for $1 million) will close in mid-June, mid-July, and mid-August 2023. The proceeds of the investment will be used for general business operations and working capital for future initiatives.

This commitment from BD1 Holdings arrives as the Company accelerates a strategic plan that includes global expansion, new revenue streams and progress in perovskites solar technology. This announcement is preceded by a series of announcements including a 300% increase in modern manufacturing capacity at a new location in Switzerland, a new $9M round of equity financing, and the inauguration of a new Center of Excellence focused on Perovskites commercialization.

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.”

Scientists from Karlsruhe Institute of Technology (KIT) have developed a new way to fabricate micro-patterned translucent perovskite solar cells that could be used in tandem solar modules intended for applications in building-integrated photovoltaics (BIPV). “While translucent perovskite multi-junction devices have been envisaged and recognized as a promising path towards high- efficiency neutral-color transparent PV, the tolerance of complex perovskite tandem stacks against extensive laser scribing has yet to be explored,” the research group said.

The researchers noted that the cells have thus far provided decent levels of power conversion efficiency while maintaining a high average visible transmittance (AVT). They used a custom-built laser scribing setup to fabricate a perovskite solar cell with n–i–p architecture and with an active area of 0.105 cm². The device is based on an indium tin oxide (ITO) substrate, a hole transport layer made of carbazole (2PACz), an electron transport layer made of buckminsterfullerene (C60), an absorber based on methylammonium lead triiodide (CH3NH3PbI3), a bathocuproine (BCP) buffer layer, and a gold (Au) metal contact.

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.