Modeling of Electrical Characteristics of Degraded Polymer Light-Emitting Diodes

Degradation of a polymer light‐emitting diode (PLED) driven under constant current is characterized by an increase of driving voltage and a decrease of luminance and efficiency. Possible causes for degradation can be a decrease of charge‐carrier mobility, a reduced charge injection by the electrodes, or the formation of charge traps. In order to disentangle these processes, numerical simulations are performed on the device characteristics of pristine and degraded PLEDs. The observed reduction in transport and luminous efficiency under current stress is simultaneously explained by the formation of hole traps. A reduction of the hole transport upon degradation is verified by transient electroluminescence measurements. The reduction in charge transport and luminous efficiency of polymer light‐emitting diodes (PLEDs) under current stress is explained by the formation of hole traps. These hole traps give rise to additional nonradiative recombination, leading to a reduction of the light output. The recombination profile shifts from the cathode to the anode and broadens during degradation.