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The Role of Long-Alkyl-Group Spacers in Glycolated Copolymers for High Performance Organic Electrochemical Transistors.

Accepted version
Peer-reviewed

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Authors

Tan, Ellasia 
Kim, Jingwan 
Stewart, Katherine 
Pitsalidis, Charalampos 
Kwon, Sooncheol 

Abstract

Semiconducting polymers with oligoethylene glycol sidechains have attracted strong research interest for organic electrochemical transistor (OECT) applications. However, key molecular design rules for high-performance OECTs via efficient mixed electronic/ionic charge transport are still unclear. Herein, we synthesize and characterize new glycolated copolymers (gDPP-TTT and gDPP-TTVTT) with diketopyrrolopyrrole (DPP) acceptor and thiophene-based (TTT or TTVTT) donor units for accumulation mode OECTs, where a long-alkyl-group (C12 ) attached to DPP unit acts as a spacer distancing the oligoethylene glycol from the polymer backbone. gDPP-TTVTT shows the highest OECT transconductance (61.9 S cm-1 ) and high operational stability, compared to gDPP-TTT and their alkylated counterparts. Surprisingly, gDPP-TTVTT also shows high electronic charge mobility in field-effect transistor, suggesting efficient ion injection/diffusion without hindering its efficient electronic charge transport. The elongated donor unit (TTVTT) facilitates the hole polaron formation more localized to the donor unit, leading to faster and easier polaron formation with less impact on polymer structure during OECT operation, as opposed to the TTT unit. This is supported by molecular dynamics (MD) simulation. We conclude that these simultaneously high electronic and ionic charge transport properties are achieved due to the long-alkyl-group spacer in amphipathic sidechains, providing an important molecular design rule for glycolated copolymers. This article is protected by copyright. All rights reserved.

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Keywords

accumulation mode, amphipathic sidechain, conjugated polymer, long-alkyl-group spacer, organic electrochemical transistor (OECT)

Journal Title

Adv Mater

Conference Name

Journal ISSN

0935-9648
1521-4095

Volume Title

Publisher