During past years, organic-based electronic devices revealed high promise to supplement the ubiquitous silicon-based electronic devices and enable new fields of applications. At the center of this development is the considerable progress regarding π-conjugated polymer semiconductors (PSCs): Due to their processability from solution, light-weight, as well as low-cost, PSCs are now evolving towards production-scale of new technologies, e.g., in organic solar cells (OSCs), organic field-effect transistors (OFETs), and organic light emitting diodes (OLEDs). Especially OFETs are of fundamental importance, as they constitute the switching units in all logic circuits and display technologies.
However, the future world is expected to be full with smart electronics and communication devices integrated in clothes, tools and even interacting with the human body, e.g., as on-skin wearable sensors. For this the electrically-active material, just as a human tissue, requires to combine several properties in addition to being charge conducting: They need to show (i) mechanical softness, (ii) capacity to repair, (iii) multimodal sensitivity, as well as (iv) biodegradability. Here, PSCs still face challenges as they are brittle and break upon applying a mechanical stress. When trying to address this issue, the existing knowledge on mechanical properties of well-established polymeric plastics, e.g., polystyrene, cannot be directly applied for several reasons, e.g., (i) the bulkiness of monomers (including long side-chains), (ii) the rigid π-conjugated backbone, (iii) the low degree of polymerization, (iv) the small quantities in which PSCs are available, etc. Moreover, these kinds of materials should not only be mechanically compliant and stretchable, but furthermore retain their charge mobility upon stretching, and withstand numerous of mechanical stretching cycles. Considering this complex problem, researchers have been developing and investigating several approaches to combine good electrical properties and mechanical compliance within one material. These approaches include (i) stress-accommodating engineering, (ii) blending of PSCs into elastic matrix, as well as (iii) molecular engineering approach.
The latter seeks to interlink mechanical and electrical properties on the molecular level, i.e., synthesize polymers that are charge conducting and stretchable. Different strategies were tested, from the modification of side chains, to the introduction of conjugation breakings spacers into the backbone. Selected works sought to incorporate stretchability and conductivity by utilizing block copolymers, i.e., covalently linking a conjugated and a non-conjugated polymer chain, resulting in a phase separation of both constituents and preserving their respective properties.
The ultimate goal of this work is to achieve an intrinsically stretchable and electrically high-performing PSC via the block copolymer approach. This is done by connecting organosilicone, namely the polydimethylsiloxane (PDMS) elastomer – possessing outstanding mechanical properties, as well as good environmental and air stability – with a conjugated diketopyrrolopyrrole (DPP)-based donor-acceptor copolymer. The final obtained structure of this polymer is a tri-block copolymer (TBC) consisting of an inner DPP-based polymer block and two outer soft PDMS polymer blocks. The content of PDMS block can be controlled and be very high (up to 67 wt%), and easy processing, e.g., via shear coating, is possible. Relatively high charge carrier mobilities – in the same range as the reference DPP-based copolymer (i.e., without outer PDMS blocks) – are retained, and the block copolymers withstands numerous stretching cycles (up to 1500 cycles) without losing electrical functionality. Finally, one of the block copolymers was successfully incorporated into a biosensor for COVID-19 antibodies and antigens detection.
Overall, the findings of this work show that the block copolymer is a highly versatile approach to obtain functional and stretchable semiconductors with high charge carrier mobilities. Block copolymers consisting of a high-performing donor-acceptor PSC and a biocompatible elastomer could contribute towards one of the long-term goals of organic electronics – the realization of mechanically compliant materials for applications in stretchable electronics (e.g., wearable sensors, electronic skin, etc.).
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:85460 |
| Date | 12 May 2023 |
| Creators | Ditte, Kristina |
| Contributors | Lissel, Franziska, Voit, Brigitte, Kleemann, Hans, Technische Universität Dresden, Leibniz-Institut für Polymerforschung Dresden e. V. |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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