Many optoelectronic devices, such as displays, photovoltaics and sensor arrays, benefit greatly by fabricating them on flexible substrates. Although flexible organic devices have many advantages, such as versatility in shape and light weight, it is not easy to mass-produce them since reactive materials such as alkali metals, which are essential to inject/extract electrons around the cathode, degrade rapidly owing to the entry of oxygen and moisture. Thus, there is a strong desire to eliminate reactive materials from devices. Here, I show the feasibility of an air-stable organic light-emitting diode (OLED), which is realized by combining an inverted stacking structure and an inert electron injection layer. Then, the first ever flexible OLED display that can emit light over one year even in the presence of oxygen and moisture is introduced. Finally, I show a novel strategy for electron injection into organic semiconductors, which is realized by forming hydrogen bonds.
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