Material Matters – Doped Organic Semiconductors

We are excited to announce the start of the Materials Seminar Series at Chalmers. The focus of the seminar lies on recent advances in materials development for existing and emerging technologies.  Our vision is to invite exciting speakers to present their newest research findings and provide a forum to discuss research questions and to meet the speaker.

Abstract:

Design and structural tuning of conjugated polymers are presented with an aim to understand the structure-property relation toward modern applications in thermoelectrics (TE) and bioelectronics. TE applications demand not only an excellent electrical conductivity, but also high Seebeck coefficient. To achieve high electrical conductivity, different doping strategies were developed, and their impact is evaluated by measuring the TE parameters. Hybrid thin films of doped conjugated polymers and inorganics offer a viable alternative to pure polymer systems.

Bioelectronics usually employs an organic electrochemical transistor (OECT) which requires a mixed ionic-electronic conductor (MIEC) capable of uptake and release of ions depending on the on or off state of the transistor. We demonstrate that the threshold voltage as well as hole injection barrier in p-type systems can be tuned using self-doped polymers and their copolymers. Here the figure of merit determined by the material parameters is the product of charge carrier mobility and volumetric capacitance in contact with the polar/aqueous medium or electrolyte. Since such MIECs usually swell in presence of the electrolyte, it can lead to change in morphology, crystallinity etc. which also influences the charge carrier mobility as well as capacitance. Therefore, detailed studies of the thin films under working conditions using a variety of methods such as EQCMD, SEC, Mott-Schottky- as well as OECT-analysis are caried out to understand the limiting parameters.

References:

1. A competitive n-Type OECT Material via Copolymerization of Electron Deficient Building Blocks;
Erhardt, MT, et al. Adv. Electron. Mater. 2023, 2300026
2. Highly Efficient Doping of Conjugated Polymers using Multielectron Acceptor Salts
Krauss, MT et al. Macromolecular Rapid Communications, 2021, 42, 2100443
3. Polydiketopyrrolopyrroles Carrying Ethylene Glycol Substituents as Efficient Mixed-Ion Conductors for Biocompatible Organic Electrochemical Transistors; Krauss, MT et al. Adv. Funct. Mater. 2021, 31, 2010048
4. Polymer Thermoelectrics: Opportunities and Challenges,
Goel and Thelakkat, Macromolecules 2020, 53, 10, 3632–3642.