Correlation between the electronic structures of transition metal oxide-based intermediate connectors and the device performance of tandem organic light-emitting devices

The impact of electronic structures on the functionality of transition metal oxide-based intermediate connectors for tandem organic light-emitting devices is investigated by studying the interfaces and the corresponding devices. For a typical transition metal oxide-based intermediate connector, consisting of a heterointerface between MoO(3) and Mg-doped tris(8-quinolinolato) aluminum (Mg:Alq(3)), it is identified that MoO(3) is essential to the charge generation and separation process, which occurs at the interface between MoO(3) and the adjacent hole-transporting layer (HTL) via electron transfer from the highest occupied molecular orbital of the HTL into the conduction band of MoO(3). In addition, the incorporation of a Mg:Alq(3) layer is indispensable to the functionality of the intermediate connector, which not only facilitates the electron injection from MoO(3) into the electron-transporting layer of the adjacent electroluminescent (EL) unit, but also blocks the leakage of holes across the intermediate connector into the HTL of the other adjacent EL unit.