Electroluminescence characterization of FOLED devices under two type of external stresses caused by bending

Conventional organic light emitting diode (OLED) devices were fabricated on a plastic substrate with the structure of aluminum (100 nm)/lithium fluoride (0.8 nm)/tris–(8-hydroxyquinoline) aluminum (Alq3) (40 nm)/N,N′-bis(naphthalen-1-yl)–N,N′-bis(phenyl)benzidine (NPB) (50 nm)/indium-tin-oxide (ITO) (100 nm)/polyethylene terephthalate (PET) (0.127 mm). The devices were then bent with three designated radii of curvature, some in a concave direction and others in a convex direction, to apply either a tensile or compressive stress to the OLED layers. The brightness was then measured while the device was bent while supplying a constant current. Atomic force microscopy (AFM) images of the OLED devices surface (the aluminum surface) after the bending tests were shown to compare the damage caused by the different type of the stresses.