Asian Scientist Magazine (Nov. 24, 2022) —Deionized water can help increase the efficiency of solar cells, a team of researchers from South Korea has found. In a recent study published in Advanced Functional Materials, Dr. Dong-Yu Kim and colleagues from Gwangju Institute of Science and Technology showed that using a certain volume of water prevents an aggregation of organic materials in solar cells, thereby increasing their performance.
An Organic Solar Cell (OSC) consists of a few layers, each having different functions. Somewhere in the middle is an active layer made up of polymers, which convert the absorbed sunlight into power by transferring high-energy electrons from the donor to the acceptor materials. However, due to the nature of organic polymers used, the conversion process is rarely efficient as both donor and acceptor polymers tend to aggregate and form a rigid structure. To minimize this effect, the polymers need to be present as a fine-dissolved active solution. The researchers tried to achieve that by using deionized water to disperse the polymers.
The team set out an experiment with three hydrophobic donor-acceptor models. They let the active solution of polymers sit in chlorobenzene, and then stirred the solution. The stirring caused vortices near the stirring rod, but that alone didn’t make the polymers well-dispersed. Then the researchers added deionized water to the solution, which created more vortices and gave the extra push for the molecules to disperse.
Adding deionized water “enables necessary physical changes without causing chemical reactions,” said Dong-Yu Kim who led the study.
Different hydrophilicity between the water and the host active solution caused them to separate from each other. Once the two phases were fully separated, the researchers removed the water, and then slot-die printed the active solution onto a thin film. “We observed that the water-treated active solution led to a more uniform active layer thin films,” said Kim. Moreover, since the morphology of the active layer directly correlated with the device performance, the researchers compared the Power Conversion Efficiency (PCE) between the water-treated and untreated OSCs. The water-treated OSCs demonstrated higher PCE than their counterparts.
Encouraged by the results, the researchers scaled up the OSCs and found notable improvements compared to non-water-treated devices. “We fabricated large-area OSC modules with an active area of 10 cm2, which showed a conversion efficiency as high as 11.92%,” Dr. Kim stated, underscoring the potential scalability of the devices.
Source: Gwangju Institute of Science and Technology ; Image: Shutterstock
The article can be found at: Introduction of Water Treatment in Slot-Die Coated Organic Solar Cells to Improve Device Performance and Stability