Manuela Wallesch, Anand Verma, Charlotte Fléchon, Harald Flügge, Daniel M. Zink, Stefan M. Seifermann, José M. Navarro, Tonya Vitova, Jörg Göttlicher, Ralph Steininger, Lothar Weinhardt, Manuel Zimmer, Markus Gerhards, Clemens Heske, Stefan Bräse, Thomas Baumann, Daniel Volz

• The development of iridium‐free, yet efficient emitters with thermally activated delayed fluorescence (TADF) was an important step towards mass production of organic light‐emitting diodes (OLEDs). Progress is currently impeded by the low solubility and low chemical stability of the materials. Herein, we present a CuI‐based TADF emitter that is sufficiently chemically stable under ambient conditions and can be processed by printing techniques. The solubility is drastically enhanced (to 100 g L−1) in relevant printing solvents. The integrity of the complex is preserved in solution, as was demonstrated by X‐ray absorption spectroscopy and other techniques. In addition, it was found that the optoelectronic properties are not affected even when partly processing under ambient conditions. As a highlight, we present a TADF‐based OLED device that reached an efficiency of 11±2 % external quantum efficiency (EQE).