Hybrid Alkyl–Ethylene Glycol Side Chains Enhance Substrate Adhesion and Operational Stability in Accumulation Mode Organic Electrochemical Transistors

Abstract

Donor–acceptor copolymers featuring electron-deficient isoindigo units and electron-rich 3,4-ethylenedioxy (EDOT) groups are presented as new materials for accumulation mode organic electrochemical transistors (OECTs). Grafting hybrid alkyl–ethylene glycol side chains on the isoindigo units of the copolymer leads to OECTs with outstanding substrate adhesion and operational stability in contact with an aqueous electrolyte, as demonstrated by their preserved performance after extensive ultrasonication (1.5 h) or after continuous on–off switching for over 6 h. Hybrid side chains outperform copolymers with alkyl only or ethylene glycol only side chains, which retain only 27% and 10% of the on currents after 40 min of on–off switching, respectively, under the same biasing conditions. These devices are promising candidates for in vitro and in vivo bioelectronics, applications where stability as well as robust adhesion of the conjugated polymer to the substrate are essential.

Synergistically Improved Molecular Doping and Carrier Mobility by Copolymerization of Donor–Acceptor and Donor–Donor Building Blocks for Thermoelectric Application

“…[ 35 ] For another, simultaneous incorporation of alkyl chains and ethylene glycol chains is expected to tune morphology and microstructure in films. [ 36–38 ] We find that the doping efficiency is improved by increasing the molar fractions of g 3 2T‐TT along polymer chains if doped under the same condition. Meanwhile the film crystallinity of random copolymers is enhanced after doping, especially, tighter π‐π stacking for strong electronic coupling is observed.…”

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

“…Organic electrochemical transistors (OECTs) are bioelectronic devices that have received considerable recent interest due to their ability to track biological activity. [ 1–10 ] Among the classes of channel materials developed for OECTs, ethylene glycol (EG)‐functionalized organic semiconductors are particularly attractive due to: i) their high OECT performance, rivalling that of poly(3,4‐ethylenedioxythiophene) (PEDOT) analog benchmarks, [ 11–13 ] ii) the general lack of post‐processing treatments and solvent additives required to achieve maximum OECT performance, [ 14,15 ] iii) their facile synthetic tunability, [ 11,16–18 ] iv) the absence of any insulating polyelectrolyte component improving their volumetric capacitance, and v) their excellent compatibility with enzymes allowing for direct detection of biologically relevant metabolites. [ 7,19 ]…”

“…Several molecular design strategies have been employed to boost the performance of glycolated semiconductors for OECTs, including: changing the EG chain length, [ 20 ] using mixed alkyl/EG solubilizing chains [ 17,21 ] and altering the aromatic moieties in the conjugated backbone. [ 4,11,12,18,22 ] The success of these strategies is typically evaluated by comparing the OECT steady‐state performance, which is accomplished by assessing the maximum transconductance ( g m ) that can be achieved in devices [ 23 ] where μ is the electronic charge carrier mobility, C * is the volumetric capacitance, W, d , and L are the channel width, depth, and length, respectively, V Th is the threshold voltage, and V G is the gate voltage.…”

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

“…The length of the alkyl unit is varied to control the swelling of the polymer and improve the electronic charge transport properties while maintaining sufficient ionic charge transport. A similar side chain engineering approach was recently employed for the design of p-type copolymers, [17,34] however is yet to be investigated for n-type OECT materials. The relative position of the alkyl unit with respect to the conjugated backbone has been shown to have significant impact on the electronic transport properties.…”