Polymer solar cells, known for their light weight and flexibility, are ideal for wearable devices. Yet, their broader use is hindered by the toxic halogenated solvents required in their production. These solvents pose environmental and health risks, limiting the appeal of these solar cells. Alternative solvents, which are less toxic, unfortunately, lack the same solubility, necessitating higher temperatures and prolonged processing times.
This inefficiency further impedes the adoption of polymer solar cells. Developing a method to eliminate the need for halogenated solvents could significantly enhance the efficiency of organic solar cells, making them more suitable for wearable technology.
In a recently published paper, researchers outline how improving molecular interactions between the polymer donors and the small molecule acceptors using side-chain engineering can reduce the need for halogenated processing solvents.
The paper was recently published in Nano Research Energy.
“Blend morphology of polymer donors and small molecule acceptors are highly affected by their molecular interactions, which can be determined by interfacial energies between the donor and acceptor materials. When their surface tension values are similar, the interfacial energies and molecular interactions between the donors and the acceptors are expected to be more favorable,” said Yun-Hi Kim, a professor at Gyeongsang National University in Jinju, Republic of Korea. “To enhance the hydrophilicity of the polymer donors and reduce molecular demixing, side-chain engineering can be a plausible avenue.”
The Role of Side-Chain Engineering
Side-chain engineering is when a chemical group, called a side chain, is added to the main chain of a molecule. The chemical groups in the side chain affect the properties of the larger molecule. Researchers theorized that adding oligoethylene glycol (OEG)-based side chains would improve the hydrophilicity of the polymer donors thanks to the oxygen atoms in the side chains. A molecule with hydrophilicity is attracted to water.
Differences in the hydrophilicity of the polymer donors and the small molecule acceptors can impact how they interact. With increased hydrophilicity of the polymer donors and improved interactions between them and the small molecule acceptors, non-halogenated processing solvents can be used without sacrificing the performance of the solar cell. In fact, polymer solar cells made with OEG-based side chains attached to a benzodithiophene-based polymer donor had a higher power conversion efficiency at 17.7% compared to 15.6%.
Enhanced Efficiency and Stability
In order to compare results, researchers designed benzodithiophene-based polymer donors with either an OEG side chain, hydrocarbon side chains, or side chains that were 50% hydrocarbon and 50% OEG. “This elucidated the effect of side-chain engineering on blend morphology and performance of non-halogenated solvent-processed polymer solar cells,” said Kim. “Our findings demonstrate that polymers with hydrophilic OEG side chains can enhance the miscibility with small molecule acceptors and improve power conversion efficiency and device stability of polymer solar cells during non-halogenated processing.”
In addition to improved power conversion efficiency, the polymer solar cells with the OEG-based side chains had enhanced thermal stability. Thermal stability is essential for scaling polymer solar cells, so researchers heated them to 120 degrees Celsius and then compared the power conversion efficiency. After 120 hours of heating, the polymers with the hydrocarbon side chains had only 60% of their initial power conversion efficiency and had irregularities on their surface, while the blend of hydrocarbon and OEG retained 84% of their initial power conversion efficiency.
“Our results can provide a useful guideline for designing polymer donors that produce efficient and stable polymer solar cells using non-halogenated solvent processing,” said Kim.
Reference: “Polymer donors with hydrophilic side-chains enabling efficient and thermally-stable polymer solar cells by non-halogenated solvent processing” by Soodeok Seo, Jun-Young Park, Jin Su Park, Seungjin Lee, Do-Yeong Choi, Yun-Hi Kim and Bumjoon J. Kim, 24 July 2023, Nano Research Energy.
DOI: 10.26599/NRE.2023.9120088
Other contributors include Soodeok Seo, Jin Su Park, and Bumjoon J. Kim of the Korea Advanced Institute of Science and Technology; Jun-Young Park and Do-Yeong Choi of Gyeongsang National University; and Seungjin Lee of the Korea Research Institute of Chemical Technology.
The Korea Institute of Energy Evaluation and Planning and the Korean National Research Foundation funded this research.
News
Completely New Use Discovered – This Traditional Herb Has Remarkable Nerve Regenerative Properties
Blessed thistle (Cnicus benedictus), a member of the Asteraceae family, thrives in our climate. This plant has been utilized for centuries as a medicinal herb, often consumed as an extract or tea to support [...]
Scientists study lipids cell by cell, making new cancer research possible
Imagine being able to look inside a single cancer cell and see how it communicates with its neighbors. Scientists are celebrating a new technique that lets them study the fatty contents of cancer cells, [...]
Antibiotic Breakthrough: Revolutionary Chinese Study Paves Way for Superbug Defeating Drugs
New research reveals that fluorous lipopetides act as highly effective antibiotics. Bacterial infections resistant to multiple drugs, which no existing antibiotics can treat, represent a significant worldwide challenge. A research group from China has [...]
Signs of Multiple Sclerosis Show Up in Blood Years Before Symptoms Appear
UCSF scientists clear a potential path toward earlier treatment for a disease that affects nearly 1,000,000 people in the United States. By Levi Gadye In a discovery that could hasten treatment for patients with multiple [...]
Advanced RNA Sequencing Reveals the Drivers of New COVID Variants
A study reveals that a new sequencing technique, tARC-seq, can accurately track mutations in SARS-CoV-2, providing insights into the rapid evolution and variant development of the virus. The SARS-CoV-2 virus that causes COVID has the unsettling [...]
No More Endless Boosters? Scientists Develop One-for-All Virus Vaccine
End of the line for endless boosters? Researchers at UC Riverside have developed a new vaccine approach using RNA that is effective against any strain of a virus and can be used safely even by babies or the immunocompromised. Every [...]
How Are Hydrogels Shaping the Future of Biomedicine?
Hydrogels have gained widespread recognition and utilization in biomedical engineering, with their applications dating back to the 1960s when they were first used in contact lens production. Hydrogels are distinguished from other biomaterials in [...]
Nanovials method for immune cell screening uncovers receptors that target prostate cancer
A recent UCLA study demonstrates a new process for screening T cells, part of the body's natural defenses, for characteristics vital to the success of cell-based treatments. The method filters T cells based on [...]
New Research Reveals That Your Sense of Smell May Be Smarter Than You Think
A new study published in the Journal of Neuroscience indicates that the sense of smell is significantly influenced by cues from other senses, whereas the senses of sight and hearing are much less affected. A popular [...]
Deadly bacteria show thirst for human blood: the phenomenon of bacterial vampirism
Some of the world's deadliest bacteria seek out and feed on human blood, a newly-discovered phenomenon researchers are calling "bacterial vampirism." A team led by Washington State University researchers has found the bacteria are [...]
Organ Architects: The Remarkable Cells Shaping Our Development
Finding your way through the winding streets of certain cities can be a real challenge without a map. To orient ourselves, we rely on a variety of information, including digital maps on our phones, [...]
Novel hydrogel removes microplastics from water
Microplastics pose a great threat to human health. These tiny plastic debris can enter our bodies through the water we drink and increase the risk of illnesses. They are also an environmental hazard; found [...]
Researchers Discover New Origin of Deep Brain Waves
Understanding hippocampal activity could improve sleep and cognition therapies. Researchers from the University of California, Irvine’s biomedical engineering department have discovered a new origin for two essential brain waves—slow waves and sleep spindles—that are critical for [...]
The Lifelong Cost of Surviving COVID: Scientists Uncover Long-Term Effects
Many of the individuals released to long-term acute care facilities suffered from conditions that lasted for over a year. Researchers at UC San Francisco studied COVID-19 patients in the United States who survived some of the longest and [...]
Previously Unknown Rogue Immune Key to Chronic Viral Infections Discovered
Scientists discovered a previously unidentified rogue immune cell linked to poor antibody responses in chronic viral infections. Australian researchers have discovered a previously unknown rogue immune cell that can cause poor antibody responses in [...]
Nature’s Betrayal: Unmasking Lead Lurking in Herbal Medicine
A case of lead poisoning due to Ayurvedic medicine use demonstrates the importance of patient history in diagnosis and the need for public health collaboration to prevent similar risks. An article in CMAJ (Canadian Medical Association [...]