Electron injection and interfacial trap passivation in solution-processed organic light-emitting diodes using a polymer zwitterion interlayer

Marta Ruscello,Wolfgang Kowalsky,Gerardo Hernandez-Sosa,Todd Emrick,Florian Ullrich,D Leonardo Gonzalez Arellano,Alejandro L Briseno,Sebastian Stolz,Annemarie Pucci,Eric Mankel,Sabina Hillebrandt

doi:10.1016/j.orgel.2017.08.014

Abstract

Abstract Here we describe the use of a polymer zwitterion as a solution-processable material that serves as the key component of the electron injection layer (EIL) in solution processed organic light-emitting diodes (OLEDs). Poly(sulfobetaine methacrylate) (PSBMA) was employed in both regular and inverted device configurations as a work-function modifier for Al and ZnO cathodes, respectively. For both architectures, PSBMA significantly improved the OLED performance when compared to reference devices without EIL in terms of turn-on voltage and luminance. In inverted devices, PSBMA showed a passivation effect on ZnO surface trap states, producing better performing and more stable devices.

Highlights

One of the most attractive features of solution-processable organic electronic materials is the possibility of using printing or coating technologies for fabricating of optoelectronic components
We describe the use of a polymer zwitterion as a solution-processable material that serves as the key component of the electron injection layer (EIL) in solution processed organic light-emitting diodes (OLEDs)
Device architectures for regular OLEDs (a) and inverted OLEDs (b); chemical structure of Poly(sulfobetaine methacrylate) (PSBMA) (c)

Summary

Introduction

One of the most attractive features of solution-processable organic electronic materials is the possibility of using printing or coating technologies for fabricating of optoelectronic components. These high-throughput technologies will allow the low-cost integration of devices such as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic photodetectors (OPDs) into flexible displays, wearables, and sensors, etc. Through a reduced energy consumption process [1e3]. A common challenge in device engineering is to select materials with suitable energy matching (i.e., between a metal electrode and semiconductor) in order to avoid energy losses, while simultaneously allowing for sequential deposition of solution-processed layers. The use of conjugated polymer zwitterions as interlayer in OLEDs and solar cells has recently been reported, showing WF reduction of up to 1 eV and improved photovoltaic performance [12e16]

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Conclusion