High hole mobility through charge recombination interface in organic light-emitting diodes

We report the effects of non-radiative charge recombination interface resulting on high hole mobility and low driving voltage characteristics in organic light-emitting devices. These effects are demonstrated in the following device architecture: hole transporting layer (HTL)/extremely deep LUMO (lowest unoccupied molecular orbital) electron transporting layer (ETL)/HTL. The extremely small gap between the high HOMO (highest occupied molecular orbital) of the HTL and the deep LUMO of the ETL leads to facilitate the hole conduction through charge recombination at the interface. The excellent hole mobility of 4.7 × 10−1 cm2/V s in this device configuration is measured by the space charge limited current method with an electric field of 0.1 MV/cm. We suggest that such a high hole mobility is attributed to the rapid coulombic interaction at the charge recombination interface in addition to the hole and electron mobilities of the individual HTL and ETL, respectively.