Solar Energy

Producing highly efficient LEDs based on 2D perovskite films

Published

4 years ago

March 11, 2021

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Producing highly efficient LEDs based on 2D perovskite films

Energy-efficient light-emitting diodes (LEDs) have been used in our everyday life for many decades. But the quest for better LEDs, offering both lower costs and brighter colours, has recently drawn scientists to a material called perovskite. A recent joint-research project co-led by the scientist from City University of Hong Kong (CityU) has now developed a 2D perovskite material for the most efficient LEDs.

From household lighting to mobile phone displays, from pinpoint lighting needed for endoscopy procedures to light source to grow vegetables in Space, LEDs are everywhere. Yet current high-quality LEDs still need to be processed at high temperatures and using elaborated deposition technologies – which make their production cost expensive.

Scientists have recently realised that metal halide perovskites – semiconductor materials with the same structure as calcium titanate mineral, but with another elemental composition – are extremely promising candidates for next-generation LEDs. These perovskites can be processed into LEDs from solution at room temperature, thus largely reducing their production cost. Yet, the electro-luminescence performance of perovskites in LEDs still has room for improvement.

Led by Professor Andrey Rogach, Chair Professor at the Department of Materials Science and Engineering at CityU, and his collaborator Professor Yang Xuyong from Shanghai University, the team has found a kind of dimmer switch: they could turn one light emission from perovskites to a brighter level!

They worked with two-dimensional (2D) perovskites (also known as Ruddlesden-Popper perovskites) and succeeded to realise very efficient and bright LEDs, with best-reported performance on both current efficiency and external quantum efficiency for devices based on this kind of perovskites. This work has now put the perovskite LEDs close on the heels of current commercial display technologies, such as organic LEDs.

The key to the powerful change lies in the addition of around 10% of a simple organic molecule called methanesulfonate (MeS).

In this study, the 2D perovskites used by the team have a nanometre level thickness. The MeS reconstructs the structure of the 2D perovskite nanosheets, while at the same time enhancing exciton energy transfer between sheets of different thicknesses. Both of these changes have greatly enhanced the electro-luminescence of the thicker, green-emitting perovskite sheets within the 2D structure.

The MeS is also useful in reducing the number of defects in the 2D perovskite structure. During the process of light production, where radiative recombination took place, part of the excitons required for the process will be “wasted” in the non-radiative recombination which produces no light. MeS reduces the number of uncoordinated Pb2+ cations, the cause for excitons to undergo the non-radiative recombination, making sure more excitons participating in light production.

The results of the research for producing better LEDs has been encouraging. The brightness of 13,400 candela/m2 at a low applied voltage of 5.5 V, and external quantum efficiency of 20.5% were recorded. This is close to the maximum that many existing LED technologies can achieve, and has almost doubled the external quantum efficiency level of 10.5% reported in their previous study two years ago.

“My CityU team has built-up its expertise on perovskite materials to a very high level in a relatively short period of time, thanks to funding support from Senior Research Fellowship by the Croucher Foundation. And already we see the benefit, especially in the outcomes detailed in this latest publication,” said Professor Rogach.

“”The achieved high brightness, excellent colour purity, and commercial grade operating efficiency mark 2D perovskites as extremely attractive materials for future commercial LEDs, and potentially also display technology. It’s a tangible outcome from both fundamental and applied research into novel nano-scale materials” he adds.

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Solar Energy

Breakthrough new material brings affordable, sustainable future within grasp

Published

9 hours 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

10 hours 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

3 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