Efficient charge generation layer for tandem OLEDs: Bi-layered MoO3/ZnO-based oxide semiconductor

Abstract

A novel oxide charge generation layer (CGL) with optical and electrical advantages for tandem organic light-emitting diodes (OLEDs) is proposed. The CGL comprises amorphous Zn-Si-O (a-ZSO) and MoO3-x. Although a-ZSO has a very small work function of 3.4 eV, it forms Ohmic contact with MoO3-x with a high work function of 6.6 eV. It is discovered that the interface state appears between a-ZSO and MoO3-x, which contributes to the formation of quasi-Ohmic contact between the two oxides with dramatically different work functions. High performance of electron and hole injection/transport is achieved in tandem OLEDs with a very small voltage drop of 0.4 V at 100 mA/cm(2\) with a twofold increase in current efficiency. This new CGL provides distinct advantages over conventional organic CGL materials with respect to processing simplicity, cost, and chemical stability. (C) 2017 Elsevier B.V. All rights reserved.