Painting with Semiconductors | Printed Electronics World

AMOLF researchers Lukas Helmbrecht and Wim Noorduin have developed a reactive ink that can be painted on an equally reactive canvas. The ink reacts with the material on the canvas and becomes a semiconductor that emits colored light, an essential part of electronic components such as LEDs. Consequently, a new way of manufacturing these electronic components is now within reach. The results of the research, a collaboration between AMOLF groups Self-Organizing Matter and Hybrid Solar Cells, will be published in Advanced Materials this week.

Imagine if you could paint a canvas by changing the canvas itself to a different color instead of painting on it. Lukas Helmbrecht and his colleagues are doing this with the new ion exchange lithography. In this technique, the “ink” reacts with the “canvas” by exchanging ions. Helmbrecht put his money where his mouth is and used this technique to spray a picture of Madame Curie. “I find it fascinating to see: the green image forms as soon as you start spraying, even though both the ink and the canvas are colorless.”

Colorful technology

Research revolves around making perovskite, a new and promising semiconductor material that is used to make items such as LEDs and solar cells. Helmbrecht and his colleagues found a way to convert a lead carbonate layer (the canvas) into a perovskite by simply “painting” it with a solution of methylammonium bromide. The latter is subject to a chemical reaction with the lead carbonate to form a green-emitting perovskite. If you are using a solution of a substance other than ink, you can paint a blue or red emitting perovskite next to it, or airbrush or print a pattern on it. For more information, see IDTechEx Conductive Ink Markets 2020-2030 Report: Predictions, Technologies, Players.

By choosing different inks, a multitude of variations in the composition of the perovskites is possible. The patterns can be created very precisely: ink drops with a size of only a few micrometers also produce dots with a size of only a few micrometers. This means that the ink will not flow. “The challenge of this research was to develop the chemical reaction and the conditions: the amount of ink, the pressure and the properties of the canvas. None of these were known, and the process will not work if they are not exactly right.” says Helmbrecht.

All in one shift

The comparison with other techniques for applying layers of perovskite to a substrate comes to mind. However, this technique is fundamentally different, explains Helmbrecht. “All traditional techniques result in different layers of perovskite side by side or on top of each other. Our method results in a single layer made up of different types of perovskite.” In addition, perovskites are usually very sensitive to treatments used with traditional methods such as etching or rinsing. These can damage the perovskite. With ion exchange lithography, these treatments are no longer needed.

“In principle, this is a much simpler method of applying a pattern of different perovskite semiconductors next to one another on a chip or an LED,” says Helmbrecht. Clean rooms or other special conditions are no longer required. The researchers have demonstrated the usefulness of ion exchange lithography using the technique to make a working LED. “That has proven the principle.” Different groups within AMOLF use this technique to create other applications.

Source and top image: AMOLF

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