Solar Energy
Entropy Boosts Efficiency in Promising New Solar Material
Entropy Boosts Efficiency in Promising New Solar Material
by Clarence Oxford
Los Angeles CA (SPX) Jul 15, 2024
Solar energy is crucial for a sustainable future. Silicon, commonly used in solar panels and electronic devices, has limitations such as high cost and difficulty in mounting on curved surfaces.
Researchers are exploring alternative materials to address these issues. One promising option is “organic” semiconductors-carbon-based materials that are abundant, cost-effective, and eco-friendly.
“They can potentially lower the production cost for solar panels because these materials can be coated on arbitrary surfaces using solution-based methods – just like how we paint a wall,” said Wai-Lun Chan, associate professor of physics and astronomy at the University of Kansas. “These organic materials can be tuned to absorb light at selected wavelengths, which can be used to create transparent solar panels or panels with different colors. These characteristics make organic solar panels particularly suitable for use in next-generation green and sustainable buildings.”
While organic semiconductors are already used in display panels for electronics like cell phones and TVs, they have not yet been widely adopted in commercial solar panels due to their lower efficiency, around 12% compared to 25% for silicon cells.
Chan explained that electrons in organic semiconductors typically bind to positive counterparts called “holes,” creating electrically neutral quasiparticles known as “excitons” when light is absorbed.
However, a new class of organic semiconductors called non-fullerene acceptors (NFAs) has changed this. Organic solar cells with NFAs can achieve nearly 20% efficiency.
Despite this progress, the reason for NFAs’ superior performance remained unclear. In a study published in Advanced Materials, Chan and his team, including graduate students Kushal Rijal (lead author), Neno Fuller, and Fatimah Rudayni, along with chemistry professor Cindy Berrie, identified a microscopic mechanism contributing to the high efficiency of NFAs.
Lead author Rijal used an experimental technique called “time-resolved two photon photoemission spectroscopy” (TR-TPPE) to measure the energy of excited electrons with sub-picosecond resolution (less than a trillionth of a second).
“In these measurements, Kushal [Rijal] observed that some of the optically excited electrons in the NFA can gain energy from the environment instead of losing energy to the environment,” said Chan. “This observation is counterintuitive because excited electrons typically lose their energy to the environment like a cup of hot coffee losing its heat to the surrounding.”
Supported by the Department of Energy’s Office of Basic Energy Sciences, the team believes this process occurs due to the quantum behavior of electrons, allowing an excited electron to exist on several molecules simultaneously. This phenomenon, coupled with the Second Law of Thermodynamics, which dictates that physical processes increase total entropy, leads to the energy gain observed.
“In most cases, a hot object transfers heat to its cold surroundings because the heat transfer leads to an increase in the total entropy,” said Rijal. “But we found for organic molecules arranged in a specific nanoscale structure, the typical direction of the heat flow is reversed for the total entropy to increase. This reversed heat flow allows neutral excitons to gain heat from the environment and dissociates into a pair of positive and negative charges. These free charges can in turn produce electrical current.”
The team suggests that this entropy-driven charge separation mechanism is key to the improved efficiency of NFA-based organic solar cells.
“Understanding the underlying charge separation mechanism will allow researchers to design new nanostructures to take advantage of entropy to direct heat, or energy, flow on the nanoscale,” Rijal said. “Despite entropy being a well-known concept in physics and chemistry, it’s rarely been actively utilized to improve the performance of energy conversion devices.”
Moreover, the KU team believes their findings could help design more efficient photocatalysts for solar-fuel production, converting carbon dioxide into organic fuels using sunlight.
Research Report:Endothermic Charge Separation Occurs Spontaneously in Non-Fullerene Acceptor/Polymer Bulk Heterojunction
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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.
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