Adhesion investigation of stacked coatings in organic light-emitting diode display architecture

• Delaminated behavior of flexible organic light-emitting diode (OLED) coatings is studied.
• Glued layer effect of OLED encapsulation on fractured energies is analyzed.
• Material properties of OLED coatings are measured by nanoindentation.
• Fracture energy of dissimilar coatings is estimated by J-integral method and VCCT.
• Validation of estimated adhesion of glue/SiN layers is made by comparing testing data.

Organic light-emitting diode (OLED) display is considered one of the promising portable electronic devices given that the application requirements for the Internet of Things are necessary. Composed of multi-stacked thin films, OLED display needs to bear external gas moisture and various mechanical loadings, such as bend, torsion, and fold. Under these mechanical loadings, OLED devices undergo numerous critical failure modes, one of which is the delamination of stacked films bonded by a glued layer of OLED encapsulation that has become an important reliability concern. Accordingly, this study uses a nonlinear finite element analysis based on fracture mechanics using J-integral and modified virtual crack closure technique. The proposed method is adopted to estimate the adhesions of several concerned interfaces of dissimilar materials bonded with glue through the index of energy release rates. To validate the reliability of the proposed simulation methodology, the adhesion measurement of glue/SiN passivation is performed through a four-point bending test. The analytic results show that a cracking energy up to 20.4 J/m2 is achieved when the initial delaminated length is ~ 10 μm and when a glue with an elastic modulus of 22 MPa is considered. In addition, a long interfacial crack length appears to promote the fracture growth of ITO/SiN stacked layers under an ultra-small bending radius of 1 mm.