Graphic representation of the printing process for the perovskite LED. Image: Claudia Rothkirch/HU Berlin.
Graphic representation of the printing process for the perovskite LED. Image: Claudia Rothkirch/HU Berlin.

Microelectronics utilize various functional materials with properties that make them suitable for specific applications. For example, transistors and data storage devices are made of silicon, and most photovoltaic cells used for generating electricity from sunlight are also currently made of this semiconductor material. In contrast, compound semiconductors such as gallium nitride are used to generate light in optoelectronic elements such as light-emitting diodes (LEDs). The manufacturing processes are also different for the various classes of materials.

Hybrid perovskite materials, which are crystals possessing a perovskite structure with both inorganic and organic components, promise simplification – by arranging the organic and inorganic components into specific structures. "They can be used to manufacture all kinds of microelectronic components by modifying their composition," explains Emil List-Kratochvil, professor of hybrid devices at Humboldt-Universität zu Berlin (HU Berlin) in Germany and head of a joint research group at HU Berlin and Helmholtz-Zentrum Berlin (HZB).

What's more, processing perovskite crystals is comparatively simple. "They can be produced from a liquid solution, so you can build the desired component one layer at a time directly on the substrate," List-Kratochvil adds.

Scientists at HZB have already shown in recent years that solar cells can be printed from a solution of semiconductor compounds – and are worldwide leaders in this technology today. Now, for the first time, the joint team of HZB and HU Berlin has succeeded in producing functional light-emitting diodes in this manner, as they report in a paper in Materials Horizons.

The research group used a metal halide perovskite for this purpose. This is a material that promises particularly high efficiency in generating light – but on the other hand is difficult to process.

"Until now, it has not been possible to produce these kinds of semiconductor layers with sufficient quality from a liquid solution," says List-Kratochvil. For example, LEDs could be printed from organic semiconductors, but they only possess modest luminosity. "The challenge was how to cause the salt-like precursor that we printed onto the substrate to crystallize quickly and evenly by using some sort of an attractant or catalyst."

The scientists chose a seed crystal for this purpose: a salt crystal that attaches itself to the substrate and triggers the formation of a gridwork for subsequent perovskite layers. In this way, they were able to create printed LEDs with far higher luminosity and considerably better electrical properties than could be achieved by previous additive manufacturing processes.

But for List-Kratochvil, this success is only an intermediate step on the road to future micro- and optoelectronics that he believes will be based exclusively on hybrid perovskite semiconductors. "The advantages offered by a single universally applicable class of materials and a single cost-effective and simple process for manufacturing any kind of component are striking," he says. He is therefore planning eventually to manufacture all important electronic components this way in the laboratories of HZB and HU Berlin.

This story is adapted from material from Helmholtz-Zentrum Berlin, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.