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.
A blend of hydrocarbon and hydrophilic oligoethylene glycol (2EG) performed better than the standard solvent when used in PSC creation, based on overall performance and thermal stability. Credit: Nano Research Energy, Tsinghua University Press
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
Pope Leo Urges Global Response to Congo’s Deadliest Ebola Outbreak
Pope Leo called for international action to address the Ebola outbreak in the Democratic Republic of Congo. The epidemic has claimed over 2,500 lives and is the nation's largest recorded outbreak. The Pope emphasized [...]
Is there a summer COVID-19 surge this year? Yep, it’s ramping up again
Hantavirus. Ebola. West Nile. Measles. And, of course, cyclospora — that stomach parasite making people miserable across the country. Americans have plenty to worry about this summer. But remember COVID-19? It may not be [...]
Natural Compound in Broccoli Could Help Treat a Rare, Incurable Neurological Disease
Swinburne researchers have discovered how broccoli could help treat an extremely rare and incurable disease that affects only about 200 Australians. A naturally occurring compound in broccoli is being investigated as a possible treatment [...]
Antibody recycling, FcRn and the next generation of biologics
FcRn plays a central role in regulating the half-life of IgG antibodies and albumin, making it a critical target in both antibody engineering and autoimmune disease therapy. This article explores the biology of FcRn, [...]
Ebola kills 2,300 in three months with no vaccine available for Congo’s deadliest ever outbreak
It’s Congo’s 17th outbreak, with a toll that has eclipsed that of the country’s 2018-2020 outbreak when 2,299 deaths out of 3,481 cases were recorded. The latest data shows 101 new cases and 33 [...]
Beyond an Agency: How AI, Creativity and Commercialization Are Converging Into a New Growth Model
At a moment when AI is forcing a fundamental rethink of how work gets done, the life sciences industry is grappling with a deeper question: what role should human creativity play in an increasingly [...]
New $60 Blood Test Detects Lung Cancer Without Costly DNA Sequencing
A simple blood test that detects chemical changes in DNA identified more than 90% of stage 2-4 lung cancers in an early study, without relying on costly DNA sequencing. Researchers at Tel Aviv University and collaborating [...]
Reducing drug development failures with human-relevant models and AI
Professor Joseph C. Wu of Stanford University explains how stem cells, human-relevant models and AI are helping researchers predict which drug candidates are most likely to succeed before clinical trials. Researchers now have access [...]
Half of vaccines are binned – ‘fridge-free’ versions could change that
Vaccines that do not need to be kept cool in a fridge have been successfully trialed in patients for the first time, say UK scientists. Currently, most vaccines need to be refrigerated or frozen [...]
Mushroom Mystery: The Fungus That Makes People See Tiny Humans
A mushroom sold in markets and served in restaurants in Southwest China has an unusual warning attached to it: cook it thoroughly, or you may start seeing tiny people. For decades, people have reported [...]
Artificial intelligence used to design brand new viruses
Artificial Intelligence has been used to design brand new viruses that are fully functional and can replicate in the laboratory, say US researchers. It is the first time whole genomes have been successfully designed [...]
Molecular Manufacturing: The Future of Nanomedicine – New book from NanoappsMedical Inc.
This book explores the revolutionary potential of atomically precise manufacturing technologies to transform global healthcare, as well as practically every other sector across society. This forward-thinking volume examines how envisaged Factory@Home systems might enable the cost-effective [...]
Moderna kicks off Phase I Ebola trial as Africa readies itself for research
If the Phase I trial is successful, Moderna plans to quickly initiate Phase II and Phase III trials of its Ebola vaccine. Moderna has initiated a Phase I trial of its mRNA Ebola vaccine [...]
3D Human Brain Tissue Model Replicates Alzheimer’s Pathology
Summary: Researchers introduced a highly reproducible three-dimensional human brain tissue model capable of replicating complex neurodegenerative processes in Alzheimer’s disease. Developed over nine years using human stem cells, the self-organizing tissue spheroids integrate functional neurons, [...]
A Common Sugar May Loosen Cancer Cells and Help Them Spread
Chemotherapy may kill most ovarian cancer cells, but the few that survive can turn dangerously active. By releasing fructose, they may help nearby tumor cells break free and spread. Researchers at The Wistar Institute [...]
COVID-19 can wake up dormant viruses in the body, large study confirms
Virus reactivations by SARS-CoV-2 could worsen initial symptoms and increase risk of Long Covid. Early in the COVID-19 pandemic, scientists noticed that a SARS-CoV-2 infection can “wake up” other, dormant viruses already present in [...]
