Solar Energy

Molecular coating enhances organic solar cells

Published

3 years ago

June 11, 2021

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Molecular coating enhances organic solar cells

An electrode coating just one molecule thick can significantly enhance the performance of an organic photovoltaic cell, KAUST researchers have found. The coating outperforms the leading material currently used for this task and may pave the way for improvements in other devices that rely on organic molecules, such as light-emitting diodes and photodetectors.

Unlike the most common photovoltaic cells that use crystalline silicon to harvest light, organic photovoltaic cells (OPVs) rely on a light-absorbing layer of carbon-based molecules. Although OPVs cannot yet rival the performance of silicon cells, they could be easier and cheaper to manufacture at a very large scale using printing techniques.

When light enters a photovoltaic cell, its energy frees a negative electron and leaves behind a positive gap, known as a hole. Different materials then gather the electrons and holes and guide them to different electrodes to generate an electrical current. In OPVs, a material called PEDOT:PSS is widely used to ease the transfer of generated holes into an electrode; however, PEDOT:PSS is expensive, acidic and can degrade the cell’s performance over time.

The KAUST team has now developed a better alternative to PEDOT:PSS. They use a much thinner coating of a hole-transporting molecule called Br-2PACz, which binds to an indium tin oxide (ITO) electrode to form a single-molecule layer. The organic cell using Br-2PACz achieved a power conversion efficiency of 18.4 percent, whereas an equivalent cell using PEDOT:PSS reached only 17.5 percent.

“We were very surprised indeed by the performance enhancement,” says Yuanbao Lin, Ph.D. student and member of the team. “We believe Br-2PACz has the potential to replace PEDOT:PSS due to its low cost and high performance.”

Br-2PACz increased the cell’s efficiency in several ways. Compared with its rival, it caused less electrical resistance, improved hole transport and allowed more light to shine through to the absorbing layer. Br-2PACz also improved the structure of the light-absorbing layer itself, an effect that may be related to the coating process.

The coating could even improve the recyclability of the solar cell. The researchers found that the ITO electrode could be removed from the cell, stripped of its coating and then reused as if it was new.

In contrast, PEDOT:PSS roughens the surface of the ITO so that it performs poorly if reused in another cell. “We anticipate this will have a dramatic impact on both the economics of OPVs and the environment,” says Thomas Anthopoulos, who led the research.

Research paper

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Solar Energy

New Layered Perovskite Structure Explored for Enhanced Optical Properties

Published

1 day ago

April 19, 2024

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New Layered Perovskite Structure Explored for Enhanced Optical Properties

by Riko Seibo

Tokyo, Japan (SPX) Apr 19, 2024

Perovskites are critically important in the field of materials science due to their distinct and varied properties arising from their unique crystal structure. These properties have potential revolutionary applications in advanced technology areas. A method to harness these properties involves precise manipulation of defects within the perovskite structure, such as missing atoms or substituting one type of atom for another.

In the realm of oxide chemistry, it’s well-established that such defects in oxides can self-organize within the crystal structure when they reach a certain threshold, leading to enhanced material properties. While this phenomenon of defect ordering is well-documented in perovskite oxides, it has not been as prevalent in hybrid halide perovskites, which consist of an organic component, a metal, and a halogen.

A recent study highlighted in ACS Materials Letters reveals findings by Associate Professor Takafumi Yamamoto and his team at Tokyo Institute of Technology, who discovered a novel defect-ordered layered halide perovskite. The research builds on earlier work where the introduction of thiocyanate ions (SCN-) into the FAPbI3 lattice led to structured defect formations. Dr. Yamamoto suggests, “Increasing the SCN concentration might amplify the formation of these defect structures, similar to those observed in vacancy-ordered oxide perovskites.”

The research involved synthesizing FAPbI3 in powder and crystal forms, using specific ratios of SCN-. When a high enough SCN- ratio was used, the resulting perovskite was FA4Pb2I7.5(SCN)0.5. This compound displayed organized defects throughout its layers-more so than its predecessor, FA6Pb4I13.5(SCN)0.5, where fewer defects were organized.

The study identifies this material as part of a ‘homologous series’-a sequence where systematic alterations to the chemical formula yield predictable changes in properties, here observed as variations in the optical bandgap correlated with defect concentration.

“This marks the first instance of a homologous series based on defect ordering in hybrid organic-inorganic perovskites,” notes Dr. Yamamoto. “Our findings set a foundational strategy for manipulating defect structures to adjust the optical properties of perovskites, offering a promising avenue for materials science innovation.”

The implications of this research are significant, potentially paving the way for new perovskite materials with tailored properties for future technological applications.

Research Report:FA4Pb2I7.5(SCN)0.5: n = 3 Member of Perovskite Homologous Series FAn+1Pbn-1I3n-1.5(SCN)0.5 with Organized Defects

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Solar Energy

Solar energy adoption challenges in rural Ethiopia

Published

1 day ago

April 19, 2024

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Solar energy adoption challenges in rural Ethiopia

by Clarence Oxford

Los Angeles CA (SPX) Apr 19, 2024

Despite decreasing costs and increasing accessibility of solar home systems, significant obstacles hinder their widespread use in remote areas of developing countries, such as Ethiopia, where they could greatly improve health and education.

Inexpensive, yet uncertified and inferior solar panels, along with limited government engagement in rural energy transition, impede access to dependable electricity for these communities.

When homes do incorporate solar energy, it replaces harmful kerosene lamps, offering a healthier, eco-friendly alternative and enabling children to study after dark.

“Understanding the dynamics of renewable energy adoption in rural sectors of the Global South is crucial,” said Yujin Lee, a doctoral student at Cornell University’s Department of City and Regional Planning and first author of a related study in Energy Policy.

Chuan Liao, the study’s senior author and assistant professor in the Department of Global Development at Cornell, emphasized, “The global shift to renewable and clean energy sources must include remote and rural populations in the developing world.”

Ethiopia’s national electrification strategy aims to power all homes within 25 kilometers of the grid by 2030. Those further away are slated for long-term off-grid solutions.

However, the prevalence of low-quality solar panels, which often fail and contribute to environmental waste, poses a barrier to adoption. Additionally, the infrequency of government visits to rural, off-grid or road-less villages leads to misinformed policies.

“Government reports often do not reflect the true situation in rural areas,” noted Lee, who found actual solar adoption rates to be markedly lower than official claims.

Lee advocates for increased governmental presence in rural communities, enhanced public engagement in energy management, and improved communication between governments, private sectors, international organizations, and end-users to support sustainable energy solutions.

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Solar Energy

The role of Floating Solar in achieving Africa’s energy targets as an alternative to dams

Published

1 day ago

April 19, 2024

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The role of Floating Solar in achieving Africa’s energy targets as an alternative to dams

by Hugo Ritmico

Madrid, Spain (SPX) Apr 19, 2024

Researchers from Politecnico di Milano have identified floating solar photovoltaics (FPV) as a viable alternative to traditional hydropower in meeting Africa’s energy goals, according to a new study published in Nature Energy. The study shows that FPV installed at existing major reservoirs could generate 20-100% of the electricity projected from planned hydropower dams across Africa.

The research, conducted using a comprehensive energy planning model, reveals that FPV is not only cost-effective compared to other renewable resources but also plays a crucial role in Africa’s energy future. “Floating solar has emerged as cost-competitive and could potentially eliminate the need for many new dams,” stated Wyatt Arnold, the lead author of the study.

A detailed analysis of the transboundary Zambezi watercourse indicated that capital investments for new dams could be more effectively utilized by constructing fewer reservoirs and augmenting them with floating solar panels. This strategy could decrease interannual variability in electricity supply by 12% and enhance resilience against long-term droughts exacerbated by climate change.

“Adopting floating solar can provide developing economies with a stable energy supply less susceptible to hydrological changes,” explained Prof. Andrea Castelletti. “Additionally, it mitigates adverse effects on downstream communities and river ecosystems compared to new dam projects.”

The study also underscores the significance of integrated resource planning and the need to consider transboundary effects in sustainable development. It promotes multisector modeling that integrates energy, agriculture, environmental protection, and economic growth within river basins.

Prof. Matteo Giuliani noted, “The strategic deployment of floating solar might outweigh potential drawbacks on reservoir uses like fishing or recreation. Yet, ongoing enhancements in FPV technology and effective planning are essential for its responsible implementation.”

While floating solar offers substantial environmental benefits, the study acknowledges challenges in technology and social acceptance that may limit its deployment. Nevertheless, these challenges are likely to be less impactful than the negative consequences of new hydropower projects, which can disrupt river ecologies, displace populations, and increase regional conflicts over water use.

Research Report:Floating solar emerges as a sustainable energy solution for Africa’s future