Mechanical analysis of organic flexible devices by finite element calculation

In recent years, organic flexible devices have been investigated extensively and sub-millimeter bending stability of organic thin film devices has been achieved by placing the active layer of the transistor on a neutral strain surface. Around the neutral strain surface, an organic thin film has a high bending durability because the in-plane tensile and compressive strain cancel each other. However, this type of highly flexible device is also destroyed or undergoes irreversible degradation when subjected to hard bending, and the breaking point is very difficult to detect experimentally. Therefore, we performed a finite element analysis of a flexible device and found a possible breaking point at the boundary between the contact electrode and the organic layer. This was the result of a strain concentration at the boundary due to the difference in Young's modulus of the organic semiconductor and Au. In addition, the shear stress is concentrated around the edge of the Au electrode. These results indicate that the most likely breaking point for this type of flexible transistor is a rupture of the organic layer at the interface with the Au electrode.