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
Scientists Just Captured the Stunning Process That Shapes Chromosomes
Scientists at EMBL have captured how human chromosomes fold into their signature rod shape during cell division, using a groundbreaking method called LoopTrace. By observing overlapping DNA loops forming in high resolution, they revealed that large [...]
Bird Flu Virus Is Mutating Fast – Scientists Say Our Vaccines May Not Be Enough
H5N1 influenza is evolving rapidly, weakening the effectiveness of existing antibodies and increasing its potential threat to humans. Scientists at UNC Charlotte and MIT used high-performance computational modeling to analyze thousands of viral protein-antibody interactions, revealing [...]
Revolutionary Cancer Vaccine Targets All Solid Tumors
The method triggers immune responses that inhibit melanoma, triple-negative breast cancer, lung carcinoma, and ovarian cancer. Cancer treatment vaccines have been in development since 2010, when the first was approved for prostate cancer, followed [...]
Scientists Uncover Hidden Protein Driving Autoimmune Attacks
Scientists have uncovered a critical piece of the puzzle in autoimmune diseases: a protein that helps release immune response molecules. By studying an ultra-rare condition, researchers identified ArfGAP2 as a key player in immune [...]
Mediterranean neutrino observatory sets new limits on quantum gravity
Quantum gravity is the missing link between general relativity and quantum mechanics, the yet-to-be-discovered key to a unified theory capable of explaining both the infinitely large and the infinitely small. The solution to this [...]
Challenging Previous Beliefs: Japanese Scientists Discover Hidden Protector of Heart
A Japanese research team found that the oxidized form of glutathione (GSSG) may protect heart tissue by modifying a key protein, potentially offering a novel therapeutic approach for ischemic heart failure. A new study [...]
Millions May Have Long COVID – So Why Can’t They Get Diagnosed?
Millions of people in England may be living with Long Covid without even realizing it. A large-scale analysis found that nearly 10% suspect they might have the condition but remain uncertain, often due to [...]
Researchers Reveal What Happens to Your Brain When You Don’t Get Enough Sleep
What if poor sleep was doing more than just making you tired? Researchers have discovered that disrupted sleep in older adults interferes with the brain’s ability to clean out waste, leading to memory problems [...]
How to prevent chronic inflammation from zombie-like cells that accumulate with age
In humans and other multicellular organisms, cells multiply. This defining feature allows embryos to grow into adulthood, and enables the healing of the many bumps, bruises and scrapes along the way. Certain factors can [...]
Breakthrough for long Covid patients who lost sense of smell
A breakthrough nasal surgery has restored the sense of smell for a dozen long Covid patients. Experts at University College London Hospitals NHS Foundation Trust successfully employed a technique typically used for correcting blocked nasal passages, [...]
Scientists Invent Plastic That Can Dissolve In Seawater In Just A Few Hours
Plastic waste and pollution in the sea have been among the most serious environmental problems for decades, causing immense damage to marine life and ecosystems. However, a breakthrough discovery may offer a game-changing solution. [...]
Muscles from the 3D printer
Swiss researchers have developed a method for printing artificial muscles out of silicone. In the future, these could be used on both humans and robots. Swiss researchers have succeeded in printing artificial muscles out [...]
Beneficial genetic changes observed in regular blood donors
Researchers at the Francis Crick Institute have identified genetic changes in blood stem cells from frequent blood donors that support the production of new, non-cancerous cells. Understanding the differences in the mutations that accumulate [...]
Shocking Amounts of Microplastics in the Brain – It Could Be Increasing Our Risk of Dementia
The brain has higher concentrations of plastic particles compared to other organs, with increased levels found in dementia patients. In a comprehensive commentary published in Brain Medicine, researchers highlight alarming new evidence of microplastic accumulation [...]
Baffling Scientists for Centuries: New Study Unravels Mystery of Static Electricity
ISTA physicists demonstrate that contact electrification depends on the contact history of materials. For centuries, static electricity has intrigued and perplexed scientists. Now, researchers from the Waitukaitis group at the Institute of Science and [...]
Tumor “Stickiness” – Scientists Develop Potential New Way To Predict Cancer’s Spread
UC San Diego researchers have developed a device that predicts breast cancer aggressiveness by measuring tumor cell adhesion. Weakly adherent cells indicate a higher risk of metastasis, especially in early-stage DCIS. This innovation could [...]
