Inkjet-printed optoelectronic devices – accessing scale and high resolution Felix Hermerschmidt 1 , Michael Hengge 2 , Selen Solak 1 , Emil J. W. List-Kratochvil 1,2 1 Humboldt-Universität zu Berlin, Germany 2 Helmholtz-Zentrum Berlin für Materialen und Energie, Berlin, Germany In recent years, inkjet printing has proven itself as a highly efficient technique for the fabrication of organic electronic devices. Offering a scalable as well as cost-effective production method, it is able to support or even replace traditional fabrication techniques such as physical vapor deposition. Inkjet printing has not only enabled precise deposition of organic inks and pastes onto more challenging substrates, such as flexible plastics, but has also facilitated the realization of indium tin oxide (ITO)-free devices making use of its high-resolution printing capabilities. These advancements have opened up new possibilities for the development of organic devices such as organic light-emitting diodes (OLEDs) or organic photovoltaics (OPVs) [1-3] . High-resolution printing has become a key focus in the field of inkjet-printed organic devices, as it directly influences device performance and visual quality. By using the inherent precision and control of the inkjet printing process as well as multistep printing with different inks, fully printed circuits can be achieved, and precise features deposited at a micrometer scale. Such fine features can then be utilized in the development of ITO-free organic devices. Indium tin oxide, conventionally used as a transparent conducting electrode in organic electronics, poses several challenges, including its inherent brittleness and scarcity of indium resources. Inkjet printing offers a good alternative by enabling the direct patterning of conductive materials as transparent electrodes. These materials, such as fine silver grids or full-area thin layers exhibit excellent electrical and optical properties, flexibility, and compatibility with low temperature sintering processes and are therefore very suitable for scalable processes [4-6] . This contribution highlights our recent work surrounding inkjet printing by presenting ITO-free electrodes manufactured from high-resolution silver grids and low-temperature plasma-cured silver layers, as well as a demonstration of a printed circuit utilizing a multistep printing and curing process in one machine. In a next step, the resolution can be further increased by accessing printing techniques that produce ultrafine grid lines in electrodes which cannot be seen anymore by the naked eye [7] . References 1. F. Hermerschmidt et al., Adv. Mater. Technol. 4, 1800474 (2019). 2. S. Pozov et al., Flex. Print. Electron. 4, 025004 (2019). 3. E. Georgiou et al., Solar RRL 2, 1700192 (2018). 4. F. Hermerschmidt et al., Adv. Mater. Technol. 3, 1800146 (2018). 5. Hengge et al., Flex. Print. Electron. 6, 015009 (2021).
6. S. Solak et al., in preparation. 7. M. Hengge et al., in preparation.
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