A joint team of HZB and Humboldt-Universität (HU) Berlin researchers has succeeded in producing functional light-emitting diodes printed from a solution of semiconductor compounds. 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 Prof. Emil List-Kratochvil, head of a Joint Research Group at HZB and Humboldt-Universität. For example, LEDs could be printed just from organic semiconductors, but these provide only 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," explains the scientist. The team chose a seed crystal for this purpose: a salt crystal that attaches itself to the substrate and triggers formation of a gridwork for the subsequent perovskite layers.
In this way, the researchers created printed LEDs that possess far higher luminosity and considerably better electrical properties than could be previously achieved using 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," says the scientist. He is therefore planning to eventually manufacture all important electronic components this way in the laboratories of HZB and HU Berlin.