Dynamic processes of charges generation in intermediate connectors for tandem organic light emitting diodes.

The role of transition metal oxides (TMOs) based intermediate connectors in tandem organic light emitting diodes (OLEDs) has been studied via capacitance-voltage and current-voltage characteristics, in order to elucidate the dynamic processes of charges generation and transport within externally applied voltages. The TMO-based intermediate connectors are composed of molybdenum trioxide (MoO 3 ) and cesium azide (CsN 3 )-doped-4, 7–diphenyl-1, 10-phenanthroline (BPhen) layers, where MoO 3 and CsN 3 are used due to low deposition temperatures. From the obtained results of capacitance and current density, charges generation in CsN 3 :BPhen/MoO 3 /NPB is proposed to the defect states in thermally evaporated MoO 3 , which offers a minimal energy offset for charges generation. Moreover, our results clearly indicate that charges generation efficiency is not only relying on the MoO 3 -NPB interface, but also influenced by CsN 3 :BPhen-MoO 3 interface. CsN 3 doped BPhen layer further improves charges separation efficiency, which finally results in favorable charges transport into the adjacent layers and ensure to function efficiently for tandem OLEDs. [ABSTRACT FROM AUTHOR]