Solar Energy
Shedding light on perovskite films
Photovoltaics decisively contributes to sustainable energy supply. The efficiency of solar cells in directly converting light energy into electrical energy depends on the material used. Metal-halide perovskites are considered very promising materials for solar cells of the next generation. With these semiconductors named after their special crystal structure, a considerable increase in efficiency was achieved in the past years.
Meanwhile, perovskite solar cells have reached an efficiency of up to 25.5 percent, which is quite close to that of silicon solar cells that are presently dominating the market. Moreover, the materials needed for perovskite solar cells are rather abundant.
The solar cells can be produced easily and at low cost and they can be used for various applications. The theoretically achievable efficiency of perovskite solar cells is about 30.5 percent.
To approach this value, optoelectronic quality of perovskite semiconductors must be further increased. In principle, materials suited for photovoltaics are expected to not only absorb light, but to also emit it efficiently. This process is known as photoluminescence. The corresponding parameter, photoluminescence quantum efficiency, is perfectly suited to determine the quality of perovskite semiconductors.
Together with scientists from the Center for Advanced Materials (CAM) of Heidelberg University and the Technical University of Dresden, researchers of KIT’s Institute of Microstructure Technology (IMT) and Light Technology Institute (LTI) have now developed a model, by means of which photoluminescence quantum efficiency of perovskite films can be determined reliably and exactly for the first time. Their results are reported in Matter.
Materials Have More Optimization Potentials than Assumed
“With the help of our model, photoluminescence quantum efficiency under solar irradiation can be determined far more precisely,” says Dr. Paul Fassl from IMT. “Photon recycling is of high importance. This is the share of photons emitted by the perovskite, which is re-absorbed and re-emitted in the thin films.”
The researchers applied their model to methylammonium lead triiodide (CH3NH3PbI3), one of the perovskites of highest photoluminescence quantum efficiency. So far, it has been estimated to amount to about 90 percent.
Model calculations, however, revealed that it is about 78 percent. The scientists explain that previous estimations did not adequately consider the effect of light scattering and, hence, underestimated the probability of photons – the quantums of light energy – leaving the film before they are re-absorbed.
“Our results show that the potential for optimization of these materials is far higher than assumed,” says Dr. Ulrich W. Paetzold, Head of the Advanced Optics and Materials for Next Generation Photovoltaics Group of IMT. The team offers an open-source application based on the model, by means of which photoluminescence quantum efficiencies of various perovskite materials can be calculated.
DGIST enhances quantum dot solar cell performance
by Riko Seibo
Tokyo, Japan (SPX) Oct 04, 2024
A research team led by Professor Jongmin Choi from the Department of Energy Science and Engineering at DGIST, in collaboration with Gyeongsang National University’s Professor Tae Kyung Lee and Kookmin University’s Professor Younghoon Kim, has developed a new method that significantly boosts the performance and longevity of perovskite quantum dot solar cells. Their innovative approach addresses a key issue: surface distortions on quantum dots that hinder solar cell efficiency.
Perovskite quantum dots are widely regarded as essential for next-generation solar cells due to their high light-to-electricity conversion efficiency and scalability. However, the process of replacing the “ligands” on their surface often causes distortions, akin to crumpled paper, that degrade solar cell performance.
The research team tackled this problem by introducing short ligands that firmly grip both sides of the quantum dots. This method effectively restores the quantum dot’s distorted surface, resembling the process of flattening crumpled paper. By smoothing the surface, they significantly reduced defects and improved both the performance and the stability of the solar cells. The power conversion efficiency rose from 13.6% to 15.3%, and the cells maintained 83% of their performance over 15 days, marking a major advancement in solar cell technology.
“Through this research, we could minimize surface defects on the quantum dots and stabilize their surfaces by newly adopting these amphiphilic ligands, thereby significantly improving the efficiency and stability of the solar cells,” explained Professor Jongmin Choi. He also noted the team’s intention to extend this approach to other photoelectric devices in the future.
This study, a collaborative effort by DGIST, Gyeongsang National University, and Kookmin University, was supported by the National Research Council of Science and Technology, the DGIST R and D Program, and the New Faculty Research Foundation at Gyeongsang National University. The findings were published in the ‘Chemical Engineering Journal’ on September 15, 2024.
Research Report:Multifaceted anchoring ligands for uniform orientation and enhanced cubic-phase stability of perovskite quantum dots
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Philippines’ Marcos opens first EV battery plant
by AFP Staff Writers
Manila (AFP) Sept 30, 2024
President Ferdinand Marcos inaugurated on Monday the first factory for electric vehicle batteries in the Philippines, calling it the “future” of clean energy.
The Australian-owned lithium-iron-phosphate factory aims to produce two gigawatt-hours of batteries per year by 2030, powering about 18,000 electric vehicles or nearly half a million home battery systems.
“We have worked very hard and tried to do our best to bring this kind of technology to the Philippines with a clear recognition that this is the future,” Marcos said in a livestreamed speech.
“As the first manufacturing plant in the Philippines for advanced iron phosphate batteries… (it) sets the stage for the Philippines to become a player in clean energy storage in our part of the world.”
Located in New Clark city north of Manila, the StB Giga Factory Inc. facility will create 2,500 local jobs and channel five billion pesos ($89.2 million) into the economy each year, Marcos said.
The investment aligns with the government’s efforts to “transition our country to renewable energy”, and would help Manila “entice more investors in renewable energy facilities in the country”, he added.
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Fire breaks out at Chinese battery giant CATL plant
by AFP Staff Writers
Beijing (AFP) Sept 29, 2024
A fire broke out Sunday at a factory belonging to Chinese battery giant CATL, which supplies electric vehicle makers including Tesla, but only a “relatively small” impact on operations is expected, the company said.
A CATL spokesperson said no injuries or casualties had occurred at the plant in the coastal city of Ningde, and that “the reasons behind this accident are still under investigation”.
Emergency services were sent to the plant to fight the fire and to organise the evacuation of any people who were inside the 15,000 square metre (160,000 square feet) site, a statement by the Dongqiao Economic and Technological Development Zone said.
Firefighters were alerted to the blaze just before 11:30 AM local time (0330 GMT).
It was not immediately clear what was produced at the plant, CATL’s base in the eastern province of Fujian, but the company said the effect of the now extinguished fire would not be significant.
“The impact to CATL’s overall production operation is relatively small,” the spokesperson said.
Videos published by the Chinese business media outlet Cailianshe, and posted on the Weibo social network, showed parts of a large white building in flames with thick gray smoke rising into the air.
AFP could not immediately verify the authenticity of the images.
CATL was founded in 2011 and produces more than a third of the electric vehicle batteries sold worldwide for automakers that include Mercedes-Benz, BMW, Volkswagen, Toyota, Honda and Hyundai.
ehl-reb/des
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