Design of ultrathin OLEDs having oxide -based transparent electrodes and encapsulation with sub -mm bending radius

Highly flexible OLEDs are demonstrated even with conventional transparent conductive oxides (TCOs) and with a multilayer gas barrier containing aluminum oxides, both of which are prone to strain-induced fracture. With careful design considering the neutral plane shift, the proposed OLEDs exhibit stable performance after 1,000 bending iterations even at a bending radius far smaller than 1 mm. © 2020 Elsevier B.V.; Highly flexible ultrathin organic light emitting diodes (OLEDs) hold vast potential as light sources particularly for wearable and imperceptible electronics. Most of the work demonstrated to date for highly flexible OLEDs, however, has relied on non-conventional transparent conductors such as conjugated polymers and has had no proper encapsulation or, if any, simple polymer-based encapsulation. We here demonstrate OLEDs that can be bent at a sub-mm radius even with conventional transparent conductive oxides (TCOs) and full encapsulation based on a multilayer gas barrier containing aluminum oxides, both of which are prone to strain-induced fracture. We realize such a small bending radis not only by adopting ultrathin substrates but also by exploiting the beneficial neutral plane shift toward the top of substrates identified in a system consisting of a ultrathin substrate and a multilayer device structure on its top. The proposed OLEDs exhibit stable performance after 1,000 bending iterations even at a bending radius far smaller than 1 mm and show similar reliability to that of glass-based reference devices even after two weeks in the acceleration test chamber. © 2020 Elsevier B.V.