Date of Award
Fall 9-5-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Jacob Ciszek
Abstract
Interlayers are used at the metal-on-organic interfaces of organic semiconductor devices to alleviate complications due to thermal metal deposition. Common methods of depositing interlayers include spin-coating, atomic layer deposition, and thermal deposition. These techniques have unintended drawbacks and limitations including by-product formation, solution degrading underlying layers, and limited compatible materials. Reactive installation of interlayers provides a way to modify the metal-organic interface while avoiding issues of the other techniques and providing secondary benefits. However, this method has yet to be utilized at the cathode-electron transport layer (ETL) interface within organic light-emitting devices (OLEDs). The reactive nitrogen of TPBi (2,2',2''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) allowed for various reactions to occur on the surface, including a ring opening with propylene oxide and acid-base reaction with trifluoroacetic acid. The addition of propylene oxide to the surface of thin film TPBi introduced a controllable oxygen-rich interlayer, confirmed by high-resolution X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX). The presence of propylene oxide lowered the contact angle and increased the wettability of TPBi while not negatively affecting a bottom-emission OLED. The reactive nitrogen of TPBi also acted as a base for deprotonation of trifluoroacetic acid leaving a carboxylate interlayer seen on polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). The carboxylate layer on the surface acted as a metal binder with an aluminum cathode, as shown in XPS and PM-IRRAS. While this work is targeted at the metal-on-organic interfaces of the ETL and cathode in OLEDS, it could be applied to a wide range of organic semiconductor devices for targeted interfacial modifications.
Recommended Citation
DePope, Kevin, "Development of Chemical Modifications to the Electron Transport Layer of Organic Light Emitting Diodes" (2025). Dissertations. 4234.
https://ecommons.luc.edu/luc_diss/4234
