Inkjet-printed ultrathin solar cells ditch rare minerals
Researchers in Saudi Arabia have developed thin, organic solar cells with a few advantages over others of their type. The new solar cells are more efficient, made using more common elements, and can be inkjet-printed onto surfaces, making them light and flexible enough to power wearable electronics.
The new solar cell design is fully printable, with different specialty inks used to produce each layer. The electrodes are made of a transparent conductive polymer called PEDOT:PSS, with a layer of an organic photovoltaic material in the middle. On the outside is a layer of parylene, a waterproof coating that helps seal the electronics against the weather.
“We formulated functional inks for each the layer of the solar cell architecture,” says Daniel Corzo, an author of the study. “Inkjet printing is a science on its own,” he says. “The intermolecular forces within the cartridge and the ink need to be overcome to eject very fine droplets from the very small nozzle. Solvents also play an important role once the ink is deposited because the drying behavior affects the film quality.”
In tests on glass plates, the team found that the new printed solar cells achieved a power conversion efficiency of 4.73 percent. That’s not very high in the wider world of solar cells, but the team says it beats the previous record for a fully-printed cell of 4.1 percent. It also outperforms other types of ultrathin solar cells. When printed onto a flexible substrate, that efficiency went down to 3.6 percent.
What they lack in overall efficiency, they make up in other ways. The inkjet printing technique makes them more scalable than other ultrathin solar cells, which are usually made using techniques like spin-coating or thermal evaporation. Plus, they don’t contain indium – a somewhat toxic and increasingly rare metal that’s often used in solar cells.
The new solar cells are also extremely lightweight, which the team demonstrated by resting them on the surface of soap bubbles. The team says that these light, flexible solar cells could be used to power small sensors, wearable electronics, and other low-energy devices.
“The tremendous developments in electronic skin for robots, sensors for flying devices and biosensors to detect illness are all limited in terms of energy sources,” says Eloïse Bihar, an author of the study. “Rather than bulky batteries or a connection to an electrical grid, we thought of using lightweight, ultrathin organic solar cells to harvest energy from light, whether indoors or outdoors.”
The research was published in the journal Advanced Material Technologies. The team describes the work in the video below.