Solar Energy

New four-terminal tandem organic solar cell achieves 16,94% power conversion efficiency

Published

9 months ago

April 9, 2024

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New four-terminal tandem organic solar cell achieves 16,94% power conversion efficiency

by Staff and Agency Writers

Paris, France (SPX) Apr 09, 2024

Researchers at ICFO have fabricated a new four-terminal organic solar cell with a tandem configuration with a 16.94% power conversion efficiency (PCE). The new device is composed by a highly transparent front cell that incorporates a transparent ultrathin silver (Ag) electrode of only 7nm, which ensures its efficient operation.

Two-terminal tandem organic solar cells (OSCs) represent one of the most promising approaches to address the transmission and thermalization losses in single-junction solar cells. These organic solar cells consist of front and rear subcells with varying bandgaps, enabling broader absorption and use of the solar spectrum. However, achieving optimal performance in such configurations demands a sufficient current balance between the two subcells. Moreover, fabricating tandem organic solar cells of these types are challenging because they need a robust interconnection layer capable of facilitating efficient charge recombination while maintaining high transparency.

The four-terminal tandem configuration has emerged as a highly efficient alternative strategy in solar cell design. Unlike the two-terminal approach, this configuration features separate electrical connections for the transparent front cell and the opaque back cell. Consequently, the issue of electrical current matching is no longer a limiting factor. This setup enables greater flexibility in selecting the bandgaps of each cell of the tandem, thereby optimizing photon absorption and enhancing the overall efficiency of solar energy production.

Now, in a new study published in the Journal Solar RRL, ICFO researchers Francisco Bernal-Texca, and Prof. Jordi Martorell describe the fabrication of a four-terminal tandem organic solar cell that has achieved a 16.94% power conversion efficiency (PCE). Central to this achievement is the fabrication of an ultrathin transparent silver electrode, a critical component that played a pivotal role in optimizing the performance of the tandem solar cell.

To fabricate the new device, the researchers first explored the organic materials destined for the photoactive layer of both cells. They examined the effectiveness of three distinct blends for the front cell, which is designed to harvest the high-energy photons. The blend that performed the best, named PM6:L8-BO, was finally chosen. For the back opaque cell, the researchers decided to use the PTB7-Th:O6T-4F blend, with a narrow bandgap, which makes it better suited to absorb the infrared part of the spectrum (low-energy photons).

After choosing the blends, the researchers used a numerical approach to design the four-tandem OSC’s final structure. They used the matrix formalism combined with the conventional inverse problem-solving methodology to find the optimal performance and the final configuration of the solar device.

The fabrication of an ultra-thin transparent silver electrode with a thickness of only 7nm was the key ingredient in the current research. This element was placed at the back of the front cell, ensuring a good light transmission to power the back cell. Conventional top Ag electrodes utilized for transparent solar cell applications typically range in thickness from 9 to 15 nm.

Its production demanded meticulous control of laboratory conditions to ensure precision and consistency. The electrode was then stacked with three dielectric layers alternating tungsten trioxide (WO3) and lithium fluoride (LiF). This photonic multilayer structure has a crucial role, because it is positioned between the two cells to facilitate efficient and uniform light distribution. “This structure exhibits a high transmission in the 750-1000 nm range and a high reflectivity in the 500-700 nm range”, researchers wrote.

“The development of a transparent silver intermediate electrode is crucial for the efficient operation of the solar cell. It must present a delicate balance, being transparent enough to allow light to reach the back cell while maintaining high electrical conductivity to ensure the optimal performance of the front cell”, said Francisco Bernal, ICFO researcher and first author of the study. “Being able to fabricate an electrode of only 7nm without observing losses in the front transparent cells is a significant advancement in the field of transparent cells”.

The researchers tested the photovoltaic performance of the device under 1 sun of illumination with a solar simulator and measured its quantum efficiency. The device achieved a 16,94% of power conversion efficiency which, to date, would be the highest reached for a four-terminal tandem organic cell. The authors of the study remark that the current official record in efficiency for organic tandem devices is 14,2% and that the last reported PCE for 4-terminal organic tandems is 6.5% .

“Our research holds potential applications in photoelectochemical cells (PEC), addressing crucial electrical requirements such as providing the necessary voltage to surpass established for driving water splitting or CO2 reduction reactions like in SOREC2 project”, explains Prof. Jordi Martorell, researcher at ICFO and SOREC2 project coordinator. “The methodology for the design and implementation of the four-terminal tandem structure could be applied to design news systems where an adequate distribution of light in the elements is crucial for the performance of a certain device”.

The researchers are currently directing their focus towards refining, tuning and enhancing the methodology and structural design tailored for applications such as solar fuels, where tandem devices hold widespread applicability. By optimizing the methodology and design strategies, researchers aim to unlock the full potential of these devices in harnessing solar energy for diverse and sustainable energy conversion processes, such as CO2 conversion and valorization.

Research Report:Four-Terminal Tandem Based on a PM6:L8-BO Transparent Solar Cell and a 7nm Ag Layer Intermediate Electrode

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Solar Energy

Breakthrough new material brings affordable, sustainable future within grasp

Published

4 days ago

December 22, 2024

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Breakthrough new material brings affordable, sustainable future within grasp

by Rashda Khan for Canepa News

Houston TX (SPX) Dec 23, 2024

While lithium-ion batteries have been the go-to technology for everything from smartphones and laptops to electric cars, there are growing concerns about the future because lithium is relatively scarce, expensive and difficult to source, and may soon be at risk due to geopolitical considerations. Scientists around the world are working to create viable alternatives.

An international team of interdisciplinary researchers, including the Canepa Research Laboratory at the University of Houston, has developed a new type of material for sodium-ion batteries that could make them more efficient and boost their energy performance – paving the way for a more sustainable and affordable energy future.

The new material, sodium vanadium phosphate with the chemical formula NaxV2(PO4)3, improves sodium-ion battery performance by increasing the energy density – the amount of energy stored per kilogram – by more than 15%. With a higher energy density of 458 watt-hours per kilogram (Wh/kg) compared to the 396 Wh/kg in older sodium-ion batteries, this material brings sodium technology closer to competing with lithium-ion batteries.

“Sodium is nearly 50 times cheaper than lithium and can even be harvested from seawater, making it a much more sustainable option for large-scale energy storage,” said Pieremanuele Canepa, Robert Welch assistant professor of electrical and computer engineering at UH and lead researcher of the Canepa Lab. “Sodium-ion batteries could be cheaper and easier to produce, helping reduce reliance on lithium and making battery technology more accessible worldwide.”

From Theory to Reality

The Canepa Lab, which uses theoretical expertise and computational methods to discover new materials and molecules to help advance clean energy technologies, collaborated with the research groups headed by French researchers Christian Masquelier and Laurence Croguennec from the Laboratoire de Rea’ctivite’ et de Chimie des Solides, which is a CNRS laboratory part of the Universite’ de Picardie Jules Verne, in Amiens France, and the Institut de Chimie de la Matie`re Condense’e de Bordeaux, Universite’ de Bordeaux, Bordeaux, France for the experimental work on the project. This allowed theoretical modelling to go through experimental validation.

The researchers created a battery prototype using the new material, NaxV2(PO4)3, demonstrating significant energy storage improvements. NaxV2(PO4)3, part of a group called “Na superionic conductors” or NaSICONs, is designed to let sodium ions move smoothly in and out of the battery during charging and discharging.

Unlike existing materials, it has a unique way of handling sodium, allowing it to work as a single-phase system. This means it remains stable as it releases or takes in sodium ions. This allows the NaSICON to remain stable during charging and discharging while delivering a continuous voltage of 3.7 volts versus sodium metal, higher than the 3.37 volts in existing materials.

While this difference may seem small, it significantly increases the battery’s energy density or how much energy it can store for its weight. The key to its efficiency is vanadium, which can exist in multiple stable states, allowing it to hold and release more energy.

“The continuous voltage change is a key feature,” said Canepa. “It means the battery can perform more efficiently without compromising the electrode stability. That’s a game-changer for sodium-ion technology.”

Possibilities for a Sustainable Future

The implications of this work extend beyond sodium-ion batteries. The synthesis method used to create NaxV2(PO4)3 could be applied to other materials with similar chemistries, opening new possibilities for advanced energy storage technologies. That could in turn, impact everything from more affordable, sustainable batteries to power our devices to help us transition to a cleaner energy economy.

“Our goal is to find clean, sustainable solutions for energy storage,” Canepa said. “This material shows that sodium-ion batteries can meet the high-energy demands of modern technology while being cost-effective and environmentally friendly.”

A paper based on this work was published in the journal Nature Materials. Ziliang Wang, Canepa’s former student and now a postdoctoral fellow at Northwestern University, and Sunkyu Park, a former student of the French researchers and now a staff engineer at Samsung SDI in South Korea, performed much of the work on this project.

Research Report:Obtaining V2(PO4)3 by sodium extraction from single-phase NaxV2(PO4)3 (1 < x < 3) positive electrode materials

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Solar Energy

Pioneering advancements in solid-state battery technology for energy storage

Published

4 days ago

December 22, 2024

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Pioneering advancements in solid-state battery technology for energy storage

by Riko Seibo

Tokyo, Japan (SPX) Dec 23, 2024

Recent strides in solid-state battery technology are setting the stage for a transformative era in energy storage. These advancements hold promise for revolutionizing electric vehicles and renewable energy systems through improved performance and safety. A focus on electrolyte innovation has been key to this progress, enabling the development of high-performance all-solid-state batteries (ASSBs).

A new review paper provides a comprehensive summary of advancements in inorganic solid electrolytes (ISEs), materials that are central to ASSBs. Researchers examined the roles of oxides, sulfides, hydroborates, antiperovskites, and halides not only as electrolytes but also as catholytes and interface layers, which collectively enhance battery performance and safety.

“We highlighted the recent breakthroughs in synthesizing these materials, honing our attention on the innovative techniques that enable the precise tuning of their properties to meet the demanding requirements of ASSBs,” said Eric Jianfeng Cheng, associate professor at Tohoku University’s Advanced Institute for Materials Research (AIMR). “Precise tuning is crucial for developing batteries with higher energy densities, longer life cycles, and better safety profiles than conventional liquid-based batteries.”

The review also delves into the electrochemical properties of ISEs, including ionic conductivity, stability, and electrode compatibility. Researchers evaluated current ASSB models and suggested emerging strategies that could drive the next generation of energy storage solutions.

However, challenges persist in the development of ASSBs, notably the limited compatibility between ISEs and electrodes, which can trigger interfacial reactions. Addressing these compatibility issues is vital to improving battery efficiency and longevity. The review outlines these challenges and provides insights into efforts aimed at overcoming them.

“Our comprehensive review underscores the importance of continued research and development in the field of solid-state batteries. By developing new materials, improving synthesis methods, and overcoming compatibility issues, current efforts are driving innovation toward practical ASSBs that could transform how we store and use energy,” Cheng added.

Research Report:Inorganic solid electrolytes for all-solid-state lithium/sodium-ion batteries: recent developments and applications

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Solar Energy

Buried interface engineering drives advances in tin-lead perovskite solar cell efficiency

Published

6 days ago

December 20, 2024

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Buried interface engineering drives advances in tin-lead perovskite solar cell efficiency

by Simon Mansfield

Sydney, Australia (SPX) Dec 20, 2024

A team led by Prof. Meng Li from Henan University’s School of Nanoscience and Materials Engineering has unveiled an innovative approach to overcoming stability and efficiency challenges in tin-lead (Sn-Pb) perovskite solar cells. The researchers’ work focuses on optimizing the buried hole-selective interface using a specially designed self-assembled material, offering major implications for single-junction and tandem solar cell technologies.

Tin-lead perovskites are valued for their narrow bandgap properties, which position them as key materials for producing high-efficiency solar cells. However, energy level mismatches and degradation at the buried interface have constrained both their performance and long-term stability. Addressing these issues, Prof. Meng’s team designed a boronic acid-anchored hole-selective contact material, 4-(9H-carbazole-9-yl)phenylboronic acid (4PBA).

Compared to conventional materials, 4PBA demonstrated superior stability and compatibility at the substrate surface. Its high adsorption energy of -5.24 eV and significant molecular dipole moment (4.524 D) improved energy level alignment between the substrate and perovskite layer, facilitating efficient charge extraction. Additionally, the interface engineered using 4PBA improved perovskite crystallization and substrate contact, reducing defects and non-radiative recombination.

These advancements enabled Sn-Pb perovskite solar cells incorporating 4PBA to achieve a power conversion efficiency (PCE) of 23.45%. The material’s reduced corrosiveness also mitigated the degradation effects typically caused by PEDOT:PSS, a widely used hole-transport material, enhancing chemical stability and storage durability. The cells retained 93.5% of their initial efficiency after 2,000 hours of shelf storage.

“This approach offers a practical path to enhancing both the efficiency and stability of Sn-Pb perovskite solar cells, addressing energy level mismatches and interfacial stability concerns,” the research team commented.

The findings provide a foundation for advancing efficient and stable Sn-Pb perovskite solar cells and highlight the importance of interface engineering in next-generation photovoltaic technologies.

Research Report:Buried Hole-Selective Interface Engineering for High-Efficiency Tin-Lead Perovskite Solar Cells with Enhanced Interfacial Chemical Stability