Researchers at Amolf have developed a new method to pattern perovskite semiconductors and insulators. In the technique, dubbed ion exchange lithography, a reactive ink is brought into contact with an equally reactive substrate. The resulting chemical ion exchange reaction yields a perovskite material, which can be used to make electronic components such as LEDs or solar cells. To demonstrate the principle, the researchers created a fluorescent painting of Marie Curie and a green LED.
The ion exchange inks can be applied using many different techniques, ranging from traditional painting with a brush to inkjet, offset and roll-to-roll printing. A wide range of variations in the composition of the perovskites, and thus their opto-electronic properties, is possible by choosing different inks.
The patterns can be created very accurately: drops of ink just a few micrometers in size also yield dots just a few micrometers in size. This means the ink doesn’t run. “The challenge of this research was developing the chemical reaction and the conditions: the quantity of ink, the pressure and the properties of the canvas. None of these were known, and the process doesn’t work if they’re not exactly right,” says Amolf researcher Lukas Helmbrecht.
There are many other ways of applying layers of perovskites to a carrier, of course. But this technique is fundamentally different, Helmbrecht explains. “All traditional techniques result in different layers of perovskite next to each other or on top of each other. Our method results in a single layer that consists of different types of perovskite.”
In addition, perovskites are usually quite sensitive to the treatments used in traditional methods, such as etching or rinsing. These can damage the perovskite. With ion exchange lithography, these treatments are no longer needed, and neither are cleanrooms or other special conditions. “In principle, this is a far simpler method for applying a pattern of different perovskite semiconductors next to each other on a chip or LED.”