Influence of the carrier mobility and charge accumulation in interfacial layers on deterioration in organic light-emitting diodes

The influence of the carrier mobility and charge accumulation in interfacial layers on the deterioration of organic light-emitting diodes (OLEDs) was investigated. There was a relationship between the deterioration of the device characteristics and the electron mobility of the emissive layer and the electron transport layer. The samples with lower electron mobilities had less degradation, whereas the samples with higher electron mobilities had more significant degradation. We simultaneously observed a decrease in the maximum capacitance, Cmax, of the OLEDs, implying that there was charge accumulation at the recombination zone in the vicinity of the emitting layer. Our study demonstrates that controlling the electron mobility in the electron transport layer is necessary to protect the device from accumulation or trapping of charges and deterioration of the luminance.