Fabrication and characterization of Ag film with sub-nanometer surface roughness as a flexible cathode for inverted top-emitting organic light-emitting devices

Abstract

An ultra-smooth Ag film with sub-nanometer surface roughness on a flexible substrate has been fabricated by a template-stripping process and its effect on the carrier injection and transport in organic light-emitting devices (OLEDs) has been investigated. The use of the ultra-smooth Ag film as an electrode results in both enhanced carried injection due to the improved contact between the electrode and the organic layer and enhanced carrier transport due to the larger grain size of the deposited organic layer on it. The ultra-smooth Ag film on the flexible substrate has been applied in inverted top-emitting OLEDs (ITOLEDs) as cathode, which exhibit improved efficiency due to the enhanced electron injection and transport. The maximum current efficiency of the ITOLEDs on the flexible substrate is 9.72 cd A⁻¹, whereas it is 6.03 cd A⁻¹ for the devices on the conventional Si substrate, which corresponds to about a 62% enhancement. Moreover, the flexible ITOLEDs keep their good performance under a small bending radius and after repeated bending.