A review paper by Khalifa University and a team of international scientists advances understanding of the latest developments underway to improve the performance and cost of flexible, polymer solar cells

On the roadmap of the world’s transition to clean energy, solar power leads the way. Every day, the sun releases more energy than humanity needs to power everything on Earth, but tapping into that power remains the challenge. Photovoltaics are electronic devices that convert sunlight into electricity, and while their cost has plummeted recently due to intense interest, challenges remain.

Researchers from Khalifa University have collaborated with a team of international researchers to conduct a review of cathode buffer layers used in organic solar cells. Their review paper, which was published in, explains the advances researchers have made in recent years in materials science to improve the overall efficiency and lifetime of this type of photovoltaic.

Dr. Vinay Gupta and Dr. Shashikant Patole, both Assistant Professors in the Khalifa University Department of Physics, undertook their review in collaboration with researchers from the CSIR-National Physical Laboratory, India, Swansea University, United Kingdom, and the University of Jammu, India.

An organic solar cell is a type of photovoltaic that uses conductive organic polymers to absorb light and produce electricity from sunshine. Most organic photovoltaic cells are polymer solar cells.

Compared to silicon-based devices, polymer solar cells are lightweight, flexible, customizable on the molecular level and inexpensive to fabricate. But these advantages are balanced by their disadvantages: they offer about one third of the efficiency of other materials and experience substantial photochemical degradation.

“The high costs involved in inorganic photovoltaic materials have prevented these technologies from having a significant impact on global energy production,” Dr. Gupta said. “Organic photovoltaics like pervoskite solar cells (PSCs) and dye-sensitized solar cells (DSSCs) are being studied as potential alternatives, but they suffer from drawbacks including low power conversion efficiency and a short lifespan with real sensitivity to the environment.”

For their work, the research team focused on the cathode buffer layer (CBL), investigating architecture, materials and mechanisms of action to provide detailed insight into the opportunities for CBL improvement.

“The primary role of a CBL is to facilitate the collection of electrons at an electrode,” Dr. Patole said. “But it also performs several other tasks in making a solar cell function smoothly, including forming an electron selective and transport interlayer, blocking reverse charge carriers, and protecting the active layer from the hot metal atoms during thermal deposition of the cathode. For efficient organic solar cells, selecting an appropriate and high quality CBL is crucial.”

Per the researchers’ findings, an ideal CBL should be good at electron extraction and transport; have a suitable energy level that facilitates electron transport with high transparency and stability; and offer compactness for use in lightweight, flexible organic solar cells. One such material used is titanium oxide, a semiconducting metal oxide favored for its unique optical properties. Research has also found that adding cesium into the titanium oxide mix further improved device performance, while zinc oxide and zirconium oxide have also been studied.

“A diverse variety of organic materials, including conjugated polymers and small molecules, have also been explored as CBL in organic solar cells,” Dr. Gupta said.

“Small molecule-based layers offer advantages thanks to their well-defined molecular weight and the easy purification process. Quantum dots have also been explored because of their tunable optical and electrical properties, however, their commercial application is hindered by their sensitivity to the environment. Still, they remain interesting as an emerging class of nanomaterials with unique properties.”

The research team found that oxides and carbonates are popular as CBLs in organic solar cells, with zinc oxide one of the most widely used CBLs in high efficiency solar cells thanks to its chemical and thermal stability, favorable electronic and optical properties, and its low-cost fabrication. Metal and alkali fluorides, including calcium, barium, and lithium, are also popular as they improve performance in extracting electrons.

Additionally, organic solar cells can only harness sunlight from a narrow range of the electromagnetic spectrum, as ultraviolet and infrared photons can degrade the photoactive layer.

While CBLs can be used to resolve these issues and increase the lifetime of the devices, a CBL would need to perform dual functions, performing its duties at the cathode level and also in protecting the photoactive layer.

It is clear from the review paper that further improvements in performance are needed to allow polymer solar cells to compete with silicon cells, but efforts are being made to improve their viability in the photovoltaic market. The research offered by the team in their review paper will help researchers around the world develop these high efficiency cathode buffer layers for improved organic solar cell devices.��

Jade Sterling
Science Writer
31 March 2022

The post Engineered Cathode Buffer Layers for Highly Efficient Organic Solar Cells appeared first on Khalifa University.

A nascent but promising solution to the world’s water scarcity problems could be water purification by direct solar vapor generation

Although desalination methods like membrane distillation and reverse osmosis have been employed to provide clean water to millions around the world, small-scale desalination for off-grid purposes remains hampered by cost and energy consumption challenges. Direct solar vapor generation is an off-grid distillation technology that, while still early stage, is attracting attention. For this reason a team of researchers from Khalifa University has been undertaking research on the topic.

Afra S. Alketbi, PhD student in Engineering, and Dr. Aikifa Raza, Research Scientist in the Department of Mechanical Engineering, developed a micro-3D printed hydrogel device to be used in direct solar vapor generation (DSVG). Their new device is portable and highly efficient, promising great potential for use in commercial DSVG systems. Alketbi and Dr. Raza collaborated with Muhammad Sajjad, PhD student , Dr. Hongxia Li, Postdoctoral Fellow, Dr. Faisal AlMarzooqi, Assistant Professor of Chemical Engineering, and Prof. TieJun Zhang, Professor of Mechanical Engineering. The results were published in the.

Direct solar vapor generation involves harvesting the heat from the sun to convert water into vapor, which is then condensed and collected to provide clean water. Sounds simple and it is: the oldest desalination technology is the solar still, a simple device that uses the energy from sunlight to purify water. Salty water is placed in the still and an angled piece of glass or plastic is placed above. The sunshine evaporates the water, which then condenses on the surface above before running down the surface to collect in a separate trough. The impurities and salt remain in the bottom of the still and the water in the trough is clean, pure drinking water. This is the basic principle behind DSVG but the key step—evaporation—is proving a roadblock for commercialization.

“Direct solar vapor generation provides a sustainable and eco-friendly solution to the current global water scarcity challenges,” Prof. Zhang said. “However, existing systems using natural sunlight suffer from low water yield and need a lot of energy to start the evaporation process. If we could find new materials that reduce the heat needed for water vaporization, we could boost this process and make it commercially viable. This is where hydrogels could help.”

Hydrogels are a 3D network of hydrophilic (water loving) polymers that can swell in water while maintaining their structure. They are dynamic and highly tunable, which makes them flexible for use at different operating conditions. In this work, KU researchers developed a temperature responsive copolymer with tunable wettability and water releasing behavior.��

They leveraged 3D-printing to create a solar-powered desalination device with micro-channels and an anisotropic, or unsymmetrical crystalline, structure. The device’s hydrophilic polymeric network can maintain an uninterrupted water supply: as the water evaporates, more is drawn into the hydrogel through capillary action, inspired by the way water moves in plants.

The KU researchers modified the top surface of their device with light absorbing materials using a novel method. Photothermal materials have been utilized in floating DSVG systems as they have the ability to absorb a high amount of solar energy. This helps regulate localized heating and produce water vapor. Materials suspended in the water absorb the sun’s energy and transfer the heat to the water wetting their surface and thereby quickly generating clean water vapor.

“Developing novel materials that can yield high amounts of water vapors utilizing less energy, in addition to efficient solar-to-thermal energy conversion, are highly desired to push forward the applications of the solar energy-water nexus,” Dr. Raza said. “Hydrogels are gaining immense popularity due to their multifunctionality and biocompatibility, as well as their unique ability to encapsulate a large amount of water.”

“Because of the superior light absorption properties and water retention/activation within our hydrogel anisotropic structure, and the rapid water movement through our 3D printed microchannel network, our device achieves a remarkable water evaporation rate without solar concentration,” Alketbi said.

“In combination with high-resolution 3D printing, our hydrogel technology empowers high-performance solar distillation while offering great opportunities for digital design and accelerated development of new desalination devices,” she added.

Manufacturing this hydrogel requires a highly specialized 3D printing technique. Recent advances in additive manufacturing allow hydrogel fabrication to overcome the limitations of conventional fabrication methods. Light-based stereolithography, used in this work, is one such technique whereby a light source—a laser or projector—cures liquid ink into solid complex architectures.����

The research group is now establishing a spin-off company with support from the to produce high-end valuable products through advanced additive manufacturing.

At KIC, the startup is currently being commercialized through a structured three-month incubation program focused on imparting the founders with business, marketing, finance and legal skills.��

Jade Sterling
Science Writer
22 February 2022

The post Floating Hydrogels Could Produce Eco-friendly Clean Water from Salty Water appeared first on Khalifa University.

For the third time in a decade, solar energy prices are tumbling in the Arabian Gulf. As demand for solar installations picks up dramatically, so falls the cost of solar energy, particularly in the Middle East.

Read Arabic story��.

When it comes to the cost of energy from new power plants, onshore wind and utility-scale solar are now the cheapest sources, costing less than gas, geothermal, coal or nuclear. Ten years ago, solar was the most expensive option for building a new power plant.

In a paper published in, KU researchers Dr. Harry Apostoleris, Post-Doctoral Fellow, Dr. Amal Al Ghaferi, Associate Professor, and Prof. Matteo Chiesa, Professor, show how local conditions and global macroeconomic factors have conspired to bring solar energy into a new realm of extreme affordability in the Middle East.

They argue that the Gulf market, especially the United Arab Emirates and Saudi Arabia, represents the leading edge of the global learning curve and offers a window into the likely near future of large-scale photovoltaics around the world.

As with most technologies, the more people invested in solar power, the cheaper it became. The Middle East has emerged as a global leader in photovoltaic deployment and pricing, with large utility-scale projects launched across the region.

In a previous study, the KU research team found that rapidly declining hardware prices, local business conditions, and access to generous financing packages were the major factors contributing to the low prices, with the market validating that assessment. Global average prices in comparable climates around the world have declined to nearly match the prices observed in the Gulf region, but now, countries in the GCC are seeing a new drop in prices. It is at this point that the researchers believe solar energy has solidified itself as the economically favorable energy source, continuing impressive price drops that began in 2016.

“If pricing at this level spreads around the world, simple business sense would suggest a rapid decarbonization of electricity generation, where coal and gas plants are retired as quickly as possible and replaced with photovoltaics, simply to save money,” explained Dr. Apostoleris. “The target of deep decarbonization by 2030 being held up by many climate scientists and advocates would suddenly enter the realm of feasibility with far less disruptive interventions than were previously believed necessary.”

Global learning curves are part of the cause of these price drops. The more that solar panels were produced, the more the technologies improved and economies of scale came into play. Fossil fuels in comparison can’t compete with this pace. Additionally, sunshine is free and in the Middle East, practically guaranteed every day. The costs of tapping into this solar power was bound to decline sharply as technology improved and the industry grew.

“The UAE leadership also deserves credit for recognizing the potential of solar energy and investing in it when many countries and entities were still sceptical,” said Dr. Apostoleris. “This is one of the main reasons why the UAE is ahead of the global curve in solar energy adoption.”

Often, the low prices are also secured as part of tenders for projects only implemented a couple years later, which further drives down prices for the projects to come after.

“Auction bids have been characterized by forward-looking cost projections—developers will tend to bid not based on the market price of hardware at the time of bidding, but on the prices they expect to pay a year or more in the future when the hardware is actually being ordered,” explained Dr. Apostoleris. “As strong downward pricing trends continue, this pattern of aggressive forward-bidding can be expected to hold.”

Additionally, the prominence of major international players in the Gulf’s solar development is helping to realize below-market costs. Large firms with an established presence in the region have�� relatively lower costs of doing business and are able to set their prices for large orders of hardware to a significant degree, and even factor in reputational elements—the ‘bragging rights’—of landing a large contract and gaining market share. Coupled with generous financing packages and a consistent solar resource, the low cost of solar energy in the Gulf begins to make sense.

“It is possible that developers accept lower margins in exchange for a benefit that larger projects provide for their overall business model,” explained Dr. Apostoleris. “The developer has its own learning curve, and building larger projects allows it to move faster down this learning curve and reduce its costs for future projects.”

For the KU researchers, the solar energy economics in the Gulf follow the same general patterns as global trends, but at a substantially advanced pace. They regard this as evidence that trends in the Gulf are best viewed not as an aberration but as an indicator of the how the global market is likely to evolve in the future.

“As the future increasingly appears to be one of previously unimaginably cheap energy, the future trajectory of this industry is exceptionally promising,” said Dr. Apostoleris. “This would herald a revolution in not only solar energy but in the energy sector generally, with a new age of ultra-cheap electricity transforming our lives, economies and environment. With such dramatic change on the horizon, it makes sense to consider the next steps to take full advantage of the coming energy transformation.”

In any energy revolution, there will be opportunities as well as challenges. Renewable energies are notoriously inconsistent throughout the day and the year, although less so in regions blessed with almost constant sunshine, such as the Middle East. The existing power grids don’t have the ability to distribute power from renewables over long distances, and storing power for use during the nights when power generation from solar is impossible is another major concern. These challenges of intermittency and geography are not insurmountable, but they do require investment to develop and build the necessary infrastructure.

“There are myriad ways to modify our energy systems to enhance the value of this low-cost solar electricity,” said Dr. Apostoleris. “This is before considering the potential of demand-side management strategies that aim to shift the energy demand curve to match the solar generation curve, minimizing the need for storage. However, this is a challenge that must be met not only from a technical perspective but also from that of society more broadly.”

It is clear that the Gulf solar market can offer a window into the likely future trajectory of photovoltaics globally. While the KU researchers point to a future of immense benefit, they also point out the challenges the market will face along the way. Thankfully, the region’s solar energy pioneers are rising to the challenge.

“Interestingly, in recent months, solar panel prices have actually risen for the first time in a decade,” added Dr. Apostoleris. “This seems to be caused by a bottleneck in the supply of polysilicon, the raw material for solar cells, as global demand increases. This might be an opportunity for the UAE to move into polysilicon production, leveraging cheap clean energy and the country’s central location to become a supplier, not just a consumer, of the solar industry.”

Researchers at Khalifa University are supporting the UAE in its advancement of regional knowledge and leadership in renewable energy, as the country announces ambitious and defined renewable energy targets. Innovative research taking place at Khalifa University is driving down costs and increasing the efficiency of solar cells, investigating the effects of climate change on renewable energy production, and even demonstrating the ability to provide solar energy 24/7.��

Jade Sterling
Science Writer
24 May 2021

The post What is Going on With Middle Eastern Solar Prices and What Does It Mean for the Rest of Us? appeared first on Khalifa University.

10-meter Diameter Prototype to Help in Energy Storage, High-Efficient Power Generation, Desalination and Other Applications

Khalifa University and Wahaj Solar (Wahaj Investment L.L.C) have signed an agreement to test and verify a patented prototype in the Concentrated Solar Power (CSP) industry at the Masdar Institute Solar Platform (MISP).

The 10-meter diameter high-flux solar furnace – the first medium-scale point solar concentrator –can focus solar energy efficiently to a lower point fixed on the ground generating a very high temperature which is easily accessible. This system is unique since the focal point is fixed on the ground while the solar disk turns around it throughout the day. This would result in many applications including low cost solar energy storage allowing for 24/7 electricity production, high efficiency in electricity production, hydrogen generation from water, desalination, as well as melting metals or sand to produce glass.

The project period is one year during which the performance of the concentrator will be tested analyzed, and certain applications demonstrated by a team led by Dr. Nicolas Calvet, Assistant Professor, College of Engineering, and Chair of the Masdar Institute Solar Platform – Khalifa University. The invention has already received favorable reviews from experts in reputable international research institutes worldwide.

Dr Arif Sultan Al Hammadi, Executive Vice-President, Khalifa University of Science and Technology, said: “The MISP is a unique world-class research facility, pushing the boundaries by being multipurpose, modular and the first-of-its-kind, bringing niche capabilities to the UAE. We welcome collaborations with industry partners that will result in cutting-edge solutions in solar power, thereby facilitating faster adoption of sustainable energy technologies. We believe testing of this innovative prototype from Wahaj Solar will further demonstrate MISP’s capabilities and help in the development of CSP components, and high-temperature thermal energy storage (TES) solutions.”

Motasim Al Daour, the majority shareholder at Wahaj Solar said: “We are working with the Masdar Institute Solar Platform at Khalifa University because we would like to take advantage of the available expertise and resources at this world class facility. In collaboration with Khalifa University, we are keen launch this potentially breakthrough invention from the UAE to the entire world in the hope of considerably contributing to the progress of the CSP technology as an alternative clean source of energy.”

The technology is already patented by Wahaj’s Dr Ayman Al-Maaitah in the US, European Union, GCC and at the World Intellectual Property Organization (WIPO) with priority protection in 150 countries worldwide.

The MISP is a unique tool for developing large scale TES systems for on-demand and ‘dispatchable’ electricity production. Initially built as a demonstration plant in 2009, the facility has been significantly modified and extended by Masdar Institute in 2014 to become a user research facility also valued by industry, capable of testing large scale TES units up to 500 kWh storage capacity. This innovative and educative research facility has already attracted several international collaborations.

Clarence Michael

News Writer

20 January 2019

The post KU and Wahaj Solar Sign Agreement to Test Innovative Prototype at Masdar Institute Solar Platform appeared first on Khalifa University.