Bottom Contact Metal Oxide Interface Modification Improving the Efficiency of Organic Light Emitting Diodes

TL;DR

This study introduces Ni-containing solution-processed metal oxide interfacial layers between ITO and PEDOT:PSS in OLEDs, significantly improving device efficiency by enhancing contact properties and morphology.

Contribution

The paper presents a novel Ni-containing MO interfacial layer that enhances bottom contact quality and efficiency in solution-processed OLEDs, demonstrating improved performance over standard devices.

Findings

12% increase in current efficiency

11% increase in luminous efficacy

Improved PEDOT:PSS morphology and hole injection

Abstract

The performance of solution-processed organic light emitting diodes (OLEDs) is often limited by non-uniform contacts. In this work, we introduce Ni-containing solution-processed metal oxide (MO) interfacial layers inserted between indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to improve the bottom electrode contact for OLEDs using the poly(p-phenylene vinylene) (PPV) derivative Super-Yellow (SY) as an emission layer. For ITO/Ni-containing MO/PEDOT:PSS bottom electrode structures we show enhanced wetting properties that result in an improved OLED device efficiency. Best performance is achieved using a Cu-Li co-doped spinel nickel cobaltite [(Cu-Li):NiCo2O4], for which the current efficiency and luminous efficacy of SY OLEDs increased, respectively, by 12% and 11% from the values obtained for standard devices without a Ni-containing MO interface modification between ITO and PEDOT:PSS. The enhanced performance was attributed to the improved morphology of PEDOT:PSS, which consequently increased the hole injection capability of the optimized ITO/(Cu-Li):NiCo2O4/PEDOT:PSS electrode.