The effects of compressive stress on the performance of organic light-emitting diodes

We investigated the effects of compressive stress on the performance of polymer light-emitting diodes (PLEDs). Vertical contraction of the PLEDs under compressive stress was induced by loading the PLEDs during operation. The current density-luminescence-voltage (J-L-V) characteristics of the PLEDs under stress were measured and compared with those of unloaded PLEDs. To explain the changes in the PLED performance due to the stress, the chemistry and electronic energy band structures of each stressed layer constituting the PLEDs were analyzed via X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS), respectively. According to the analysis, an irreversible deterioration in the fluorescent characteristics of the active layer and an increased electron energy barrier between the layers of the PLEDs were induced by the applied stress, which resulted in the significant degradation of the J-L-V characteristics.