Low-Molecular-Weight Organic Light-Emitting Diodes Aiming for Low-Voltage Driving

—High Electron Injection E.ciency, Charge Transport Mechanism, and Material Synthesis—

Abstract

In organic light-emitting diodes (OLEDs), realization of highly efficient electron injection is a key issue for achieving high energy conversion efficiency. In this paper, we elucidated mechanism of the efficient electron injection using a cathode layer composed of an ultra-thin layer of Cs, Rb, K, Na, Li and Ca capped with an aluminum back electrode. In particular, we focused on the electron injection mechanism at the interface between an organic layer and the cathode layer by changing the thickness of the low work function metal layer. Further, we demonstrate efficient electron injection and transport using a novel electron transport layer composed of Cs and phenyldipyrenylphosphine oxide (POPy₂) co-deposited layer.