At present, many strategies exist for enhancing the performance and stability of organic solar cells or OSCs. Nonetheless, a problem remains the difficulty of controlling the morphology of the active layers in such organic cells when scaling up to large areas.
According to a Phys.org report, OSCs, which use organic polymers to convert sunlight into electricity, have been given substantial attention for their desirable properties as next-generation sources.
Such properties include its lightweight nature, scalability, flexibility, and high-power conversion efficiency of around 19 percent.
This makes it quite a challenge to obtain high-quality active layer thin films, then, in turn, fine-tune the device's efficiency.
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In this cross-section of an organic photovoltaic cell, light passes through the upper layers (from the top down, glass, indium tin dioxide, and thermoplastic). It generates a photocurrent in the polymer-fullerene layer. Channels formed by polymers (tan) and fullerenes (dark blue) allow an electric current to flow into the electrode at the bottom.
Water Treatment
In a new study, a research team from Gwangju Institute of Science and Technology, Korea, set out to solve this problem.
In their research, published in Advanced Functional Materials, they recommended a solution that appears rather counterintuitive at an initial glance, using water treatment to regulate the active layer morphology.
Water is known for hindering the organic electronic devices' performance since it stays in the "trap states" of the organic material, blocking the charge flow and degrading the device's performance.
Nevertheless, the team featured that using water instead of an organic solvent-based active solution as a treatment method would enable essential physical changes minus causing reactions, Professor Dong-Yu Kim, who headed the study explained.
Hydrophobic Active Solution
The study investigators opted for the polymers PTB7-Th and PM6 as donor materials and EH-1IDTBR and Y6 as acceptor materials for the active layer.
The team noticed that inducing a vortex to mix the acceptor materials and donor in the active solution could result in a well-mixed active solution, yet it was not enough.
The active solution was hydrophobic, and the study authors used deionized or DI water and vortices to stir the solution.
They let the acceptor materials and donors in chlorobenzene, host active solution, overnight, and then added to the solution, DI water,l and stirred it, creating tiny vortices.
Large-Area OSC Modules
Because of the solution's hydrophobic nature, the water pushed on the acceptor molecules and donor, causing them to dissolve more finely into the solution.
Then, they let it rest, causing the water to separate from the solution. This water was then taken out, and the water-treated active solution was used to prepare the thin films of F, fullerene, NF, fullerene, and Hamd -NF high-efficiency non-fullerene.
The authors then investigated the photovoltaic performance of such thin films in a slot-die-coated inverted OSC configured and compared them with those for OSCs minus water treatment.
A similar ScienceDaily report specified that the team observed that the active solution treated with water resulted in a more uniform active layer of thin films, showing higher power conversion efficiencies than water-treated ones.
Furthermore, the researchers fabricated large-area OSC modules with an active area of 10 cm2, showing a conversion efficiency as high as 11.92 percent for water-treated H-NF films, explained Professor Kim.
Related information about organic solar cells is shown on Michigan Engineering's YouTube video below:
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