Solar Energy

Juelich scientists uncover key efficiency mechanism in perovskite solar cells

Published

9 months ago

January 11, 2024

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Juelich scientists uncover key efficiency mechanism in perovskite solar cells

by Robert Schreiber

Berlin, Germany (SPX) Jan 11, 2024

Researchers at Forschungszentrum Julich have recently unveiled a novel aspect of perovskite solar cells, potentially unlocking the secret behind their high efficiency. This discovery, detailed in a study published in Nature Materials, centers on the unique behavior of charge carriers within these cells, diverging from conventional semiconductor laws.

Perovskite solar cells, known for their cost-effectiveness and impressive efficiency, have rapidly evolved over the past decade. Their efficiency has soared to over 25%, matching that of traditional silicon-based solar cells. Despite challenges in stability, these cells remain a focal point in photovoltaic research due to their potential for further efficiency improvements.

Thomas Kirchartz, an electrical engineer and head of the organic and hybrid solar cells group at Forschungszentrum Julich’s Institute of Energy and Climate Research, emphasizes the importance of understanding charge carrier dynamics. “An important factor here is the question of how long excited charge carriers remain in the material, in other words their lifetime,” Kirchartz explains. “Understanding the processes is crucial to further improving the efficiency of perovskite-based solar cells.”

In solar cells, photons dislodge electrons, propelling them from the valence band to the conduction band, enabling them to contribute to electrical energy generation. Their effectiveness depends largely on their lifetime, allowing them to traverse the absorber material to the electrical contact. However, defects in the crystal lattice, known as recombination, can cause these electrons to fall back to lower energy levels, ceasing their contribution to current flow. This process is the primary loss mechanism in solar cells.

Kirchartz notes that traditionally, recombination is thought to be mainly triggered by deep defects located between the valence and conduction bands. These defects are accessible to both excited electrons and holes, reducing their utility in electricity generation. This assumption holds for most solar cells.

However, the team’s latest research challenges this notion for perovskite solar cells. They discovered that shallow defects, located close to the valence or conduction band, are more critical in determining the efficiency of these cells. “The cause of this unusual behavior has not yet been fully clarified,” Kirchartz adds. He speculates that deep defects might not exist in these materials, possibly contributing to their high efficiency.

This groundbreaking observation was made possible through an innovative measurement technique developed by Kirchartz and his team. The new transient photoluminescence measurement method boasts a significantly expanded dynamic range compared to traditional methods. This advancement is akin to HDR (High Dynamic Range) in photography, where multiple images at different exposure levels are combined for a more detailed picture. In this case, signals with varying amplification levels create a richer data set.

Research Report:Shallow defects and variable photoluminescence decay times up to 280 us in triple-cation perovskites

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Solar Energy

UK announces new investment in green energy projects

Published

1 day ago

October 11, 2024

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UK announces new investment in green energy projects

by AFP Staff Writers

London (AFP) Oct 10, 2024

The UK government on Thursday announced that it had secured more than �24 billion ($31.3 billion) of private investment in green energy projects, as it gears up for an international investment summit.

Prime Minister Keir Starmer called the investments “a huge vote of confidence” in his Labour government and its long-term growth plans, despite a stuttering start in power since the party’s election win in July.

Labour, in opposition for 14 years, has vowed to revitalise the UK economy, which it claims faltered badly during successive Conservative administrations since 2010.

Central to its plans is green energy, to transition the country away from polluting fossil fuels towards renewables such as wind, wave and solar, to meet net-zero targets.

But Starmer and his finance minister Rachel Reeves have been accused of scaring off investors by relentless talk of a dire economic inheritance from the Tories and warnings about tough remedial measures to come.

Spain’s Iberdrola, which owns UK energy provider Scottish Power, said it was doubling its investment in the UK over the next four years to �24 billion.

Denmark’s Orsted is investing �8 billion and Portugal’s Greenvolt �2.5 billion, Downing Street said in a statement.

The announcements come after a record 131 new green infrastructure projects were awarded at auction last month, including plans for Europe’s two biggest offshore windfarms.

Starmer said creating the right conditions was key to boosting growth and that the International Investment Summit on Monday would be a “springboard” to do so.

The UK premier and Reeves are both slated to speak at the meeting in central London.

Labour announced its green energy strategy in July, including Great British Energy, a public-owned body that intends to spur investment in domestic renewable projects.

Great British Energy will receive �8.3 billion over the next five years.

Last week, the government announced nearly �22 billion of investment over 25 years to support three carbon capture projects in northeast and northwest England.

It has also lifted a ban on onshore wind projects in England, introduced after opposition from local residents.

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Solar Energy

Streamlined perovskite solar cells offer path to cheaper, more efficient energy

Published

1 day ago

October 11, 2024

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Streamlined perovskite solar cells offer path to cheaper, more efficient energy

by Simon Mansfield

Sydney, Australia (SPX) Oct 11, 2024

Researchers at City University of Hong Kong (CityUHK) have developed a new fabrication method that enhances the efficiency, stability, and affordability of perovskite solar cells, bringing them closer to commercial viability.

Published in ‘Science’, this study highlights how a simplified device structure designed by the CityUHK team could pave the way for future industrial-scale production of perovskite solar cells, improving their reliability and reducing costs.

“The improvements in stability and the simplification of the production process of perovskite solar cells represent a significant step forward in making solar energy more accessible and affordable,” said Professor Zhu Zonglong from the Department of Chemistry at CityUHK. Perovskite, the key material in these solar cells, effectively converts sunlight into electricity.

The team’s advancements focus on two innovations. First, they integrated hole-selective materials with the perovskite layers, streamlining the manufacturing process. Second, they replaced traditional organic materials with an inorganic electron transport layer, tin oxide, which significantly improves the solar cells’ operational stability. “The device structure reported in this study represents the most simplified architecture in the current field of perovskite solar cells,” explained Dr. Gao Danpeng, a co-author and postdoctoral researcher at CityUHK. This innovation reduces production costs by eliminating the need for an organic transfer layer, simplifying manufacturing.

These developments have resulted in power conversion efficiencies exceeding 25%, with the solar cells maintaining over 95% efficiency after 2,000 hours of continuous testing, according to Professor Zhu. This performance surpasses that of traditional perovskite solar cells, meeting key industry standards for longevity.

The findings offer new opportunities for researchers in materials science and renewable energy, with potential impacts for solar cell manufacturers and consumers alike. The study also emphasizes the environmental and policy implications, as this research could support the shift toward more sustainable energy sources, reducing fossil fuel reliance and promoting renewable energy.

In the next phase, the CityUHK team plans to scale up the technology by applying this structure to larger perovskite solar modules, aiming to enhance both efficiency and scalability.

This research was conducted in collaboration with the National Renewable Energy Laboratory and Imperial College London, reflecting the global effort toward sustainable energy solutions. “With the potential to be implemented in solar energy systems within the next 5 years, this research is a critical step towards achieving more sustainable and environmentally friendly energy production globally,” added Professor Zhu.

Research Report:Long-term stability in perovskite solar cells through atomic layer deposition of tin oxide

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Solar Energy

China’s solar goes from supremacy to oversupply

Published

2 days ago

October 10, 2024

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China’s solar goes from supremacy to oversupply

By Oliver HOTHAM

Beijing (AFP) Oct 10, 2024

Strong state support and huge private investment have made China’s solar industry a global powerhouse, but it faces new headwinds, from punitive tariffs abroad to a brutal price war at home.

Officials meeting in Baku next month for the COP29 summit hope to agree on new finance targets to help developing countries respond to climate change, including ditching fossil fuels.

Last year, countries agreed to triple global installed renewable energy capacity by 2030.

China is installing almost twice as much solar and wind power as every other country combined.

And it dominates the market.

It makes eight out of every 10 solar panels and controls 80 percent of every stage of the manufacturing process.

It is also home to the world’s top 10 suppliers of solar panel manufacturing equipment, and its related exports hit a record $49 billion last year, according to Wood Mackenzie.

That supremacy is not accidental: Chinese state support has been key, analysts say.

Beijing invested over $50 billion in new solar supply capacity from 2011 to 2022, according to the International Energy Agency.

The industry has also benefited from access to cheap raw materials, readily available capital from state-owned banks, and huge engineering manpower.

“Chinese producers were ahead of everyone else on cost,” said Lauri Myllyvirta, co-founder of the Centre for Research on Energy and Clean Air, a climate think tank.

“That meant new investment takes place in China, because that’s where it’s most competitive,” he told AFP.

The focus has driven a “steep learning curve… both in solar cell technology and manufacturing know-how”, added Johannes Bernreuter, a longtime solar industry analyst.

That in turn has created “an efficient industry ecosystem”, he said.

– ‘Overcapacity’-

As countries around the world race to convert their power systems, China’s solar supremacy has become a growing concern.

The United States and other Western countries have accused Beijing of deliberate “overcapacity” and flooding global markets with cut-price solar exports intended to undercut competition.

Washington has doubled tariffs on Chinese panels to 50 percent, part of a broader package targeting $18 billion worth of Chinese imports in strategic sectors including electric vehicles, batteries, critical minerals and medical products.

The European Union is also probing Chinese-owned solar panel manufacturers for allegedly receiving unfair subsidies.

Most US solar panel imports now come from Southeast Asia, but Washington says Chinese manufacturers have relocated operations there to circumvent barriers.

China also accounts for almost all of Europe’s imports of solar panels from outside the bloc.

That means many markets will struggle to catch up “with two decades of very forceful and very successful industrial policy in China”, said Myllyvirta.

China’s solar industry faces its own struggles though, beyond trade barriers in the West.

The sector’s supersonic expansion has overleveraged the domestic industry, overloaded China’s grid and sparked a brutal price war, experts say.

Industry leaders have reportedly warned of an “ice age” and urged government intervention to stem slumping prices, but there has been little sign of relief.

This year saw a wave of bankruptcies, and new solar projects fell by over 75 percent in the first half of 2024, an industry group said in July.

– ‘Lots of companies will fail’ –

The price wars, which are so fierce that solar export earnings fell last year despite volumes hitting a new high, are like a “snake eating its own tail”, warned analyst David Fishman.

Companies get stuck “in this circle of competition where whoever is able to endure the pain for longest comes out as the victor,” said Fishman, a senior manager at the Lantau Group specialising in China’s power sector.

“Lots of companies will fail along the way.”

And while the manufacturing glut has helped China hit a wind and solar installation target nearly six years ahead of schedule, the country’s grid is struggling to keep up.

Increasingly, renewable supply is being blocked to prevent the grid from becoming overwhelmed, a process known as curtailment.

Solar curtailment rose four percent in the first quarter of 2024 from a year earlier, according to Fitch Ratings.

Authorities will soon be forced to “stop approving new projects or allowing projects to connect to the grid if it means curtailment rates are at risk of going higher”, Fishman said.

“They’ve got to build,” he added. “They have to catch up.”

Blocked in the West and running out of track at home, China’s solar is seeking new markets, and this year, Europe was overtaken by Asia as the biggest export market for solar products, according to an industry body.

Exports to Africa also soared 187 percent year-on-year in 2023, though the continent still buys a small fraction compared to Europe, according to energy think tank Ember.

The industry is now in a “restructuring and shakeout phase”, said Bernreuter.

After that, “the Chinese solar industry will march on with unperturbed pace and a more global manufacturing footprint”.

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