Scientists have developed a solar cell that can bend and soak in water

Researchers and their partners at the RIEKN Creative Physical Science Research Center have created a flexible and waterproof organic photovoltaic film. This innovative thin film can integrate solar cells into clothing, maintaining functionality even in rainwater or washing cycles.

One of the potential uses of organic photovoltaic technology is to manufacture wearable electronic devices that can be attached to clothing, such as monitoring medical devices without the need for battery replacement. However, researchers have found that achieving waterproofing without the use of additional layers is very difficult, as the additional layer reduces the flexibility of the film.

Breakthroughs in Photovoltaic Technology
Now, a group of scientists publishing research results in Nature Communications can precisely achieve this. The challenge they face is overcoming a key limitation of previous equipment, which is that it is difficult to make it waterproof without reducing flexibility. Photovoltaic films typically consist of several layers. One layer is the active layer, which captures energy of a certain wavelength from sunlight and uses this energy to separate electrons and "electron holes" into cathodes and anodes. Then, electrons and holes can be reconnected through circuits to generate electrical energy. In previous devices, the layers for transmitting electron holes were usually generated sequentially through a layered approach.

But in the current work, researchers deposit the anode layer (in this case, the silver electrode) directly onto the active layer, thereby forming better adhesion between layers. They used a hot annealing process to expose the film to air at 85 degrees Celsius for 24 hours. The first author of the paper, Xiong Sixing, said, "Forming a thin film layer is very challenging, but we are pleased to have completed this task and ultimately be able to produce a thin film with a thickness of only 3 microns. We look forward to seeing the test results."

The results seen by the group from the test are very encouraging. Firstly, they completely immersed the film in water for four hours and found that its performance still had 89% of its initial performance. Then, they stretched the film 30% underwater 300 times and found that even with such punishment, the film still maintained 96% performance. In the final test, they placed the film in the washing machine for cyclic washing, and the film withstood the test, which was unprecedented before.

One of the corresponding authors of the paper, Kenjiro Fukuda, said, "What we have created is a method that can be widely used. Looking ahead, by improving the stability of the device in other aspects, such as exposure to air, strong light, and mechanical stress, we plan to further develop our ultra-thin organic solar cells to enable them to be used in truly practical wearable devices."

Source: sciechdaily