Side Chain Redistribution as a Strategy to Boost Organic Electrochemical Transistor Performance and Stability

Abstract

A series of glycolated polythiophenes for use in organic electrochemical transistors (OECTs) is designed and synthesized, differing in the distribution of their ethylene glycol chains that are tethered to the conjugated backbone. While side chain redistribution does not have a significant impact on the optoelectronic properties of the polymers, this molecular engineering strategy strongly impacts the water uptake achieved in the polymers. By careful optimization of the water uptake in the polymer films, OECTs with unprecedented steady‐state performances in terms of [μC*] and current retentions up to 98% over 700 electrochemical switching cycles are developed.

The Effect of Alkyl Spacers on the Mixed Ionic‐Electronic Conduction Properties of N‐Type Polymers

“…[15][16][17][18][19][20][21] Through careful engineering of the side chain length and density, p-type polymers can now operate in aqueous-based OECTs with µC* products higher than 100 F cm −1 V −1 s −1 . [15,16,22] The first example of a n-type OECT operating in aqueous electrolytes [18] was accomplished by functionalization with a polar EG-based side chain of a widely studied n-type backbone motif, the naphthalene tetracarboxylic diimide-bithiophene (NDI-T2), [23] forging new directions for OECT-based technologies. One research area that has greatly benefited from electron-transporting OECT materials is enzymatic sensing of metabolites such as lactate or glucose.…”

A Low‐Swelling Polymeric Mixed Conductor Operating in Aqueous Electrolytes

“…However, efficient ion uptake/flow is often accompanied by an intrinsic volumetric expansion of the active material, rendered more pronounced in case excess solvent is also incorporated into the material during ion uptake. Such an expansion/shrinkage can compromise mechanical integrity during cycling, limiting device stability as was shown for batteries [ 4 ] as well as for bioelectronics devices [ 5,6 ] —and pronounced volumetric changes associated with ion insertion/intercalation have been recognized as one of the major limitations in lithium ion‐based technologies. [ 7 ]…”

Polaron Delocalization in Donor–Acceptor Polymers and its Impact on Organic Electrochemical Transistor Performance

“…[5][6][7][8][9][10][11][12][13] While advancements in device architecture have significantly contributed to the progress in OECTs, [14][15][16] the development of novel and carefully tailored channel materials has also been ac rucial component for consistently reaching higher performances. [17][18][19][20][21][22] Amongst the several classes of OECT channel materials developed, ethylene glycol (EG) functionalized organic semiconductors,h ave shown to be particularly promising candidates due to:(i) their lack of any insulating polyelectrolyte phase increasing the density of electronic charges that can be accumulated thus boosting their volumetric capacitance [21] (ii)t heir tendency to achieve optimum OECT performances without the need of any solvent-additives and post-processing treatments, [21,23] (iii) their excellent OECT operation, ranking them amongst the highest performing channel materials reported to date, [18,20,22,24] (iv) their good enzyme compatibility enabling for the direct detection of biologically relevant ions and molecules foregoing the need of any mediators [10] and (v) their facile synthetic tunability at the molecular scale.G iven the promise of EG functionalized organic semiconductors, several different molecular engineering strategies have been pursued to maximize their performance in OECTs. [25,26] Broadly speaking these can be categorized into those focusing on the modification of the side chains [22,[27][28][29][30][31][32] and those altering the aromatic building blocks of the conjugated polymer backbone.…”