Toward fully flexible multilayer moisture-barriers for organic light-emitting diodes

Flexible organic light-emitting diodes require flexible thin-film encapsulation to ensure both a long lifetime and flexibility of the device. Although an aluminum oxide layer grown by atomic layer deposition can protect the device from oxidative species, such as moisture, it does not provide sufficient flexibility for a flexible device. Thus, organic-inorganic multilayer structures were prepared and tested for both the moisture-barrier property and flexibility to achieve fully flexible thin-film encapsulation for organic light-emitting diodes. The flexible thin-film encapsulation developed in this study resulted in an initial water vapor transmission rate of 3 × 10−4 g/m2/day that decreased by only 10% even after a 10 000 severe bending cycles at a bending radius of 0.3 cm. This result was possible by reducing the thickness of the aluminum-oxide sub-layer as low as possible down to only 1 cycle of atomic layer deposition and placing it in a neutral stress plane. Theoretical estimations of tensile strain supported the experimental results.