Semiconducting Small Molecules as Active Materials for p‐Type Accumulation Mode Organic Electrochemical Transistors

Abstract

A series of semiconducting small molecules with bithiophene or bis‐3,4‐ethylenedioxythiophene cores are designed and synthesized. The molecules display stable reversible oxidation in solution and can be reversibly oxidized in the solid state with aqueous electrolyte when functionalized with polar triethylene glycol side chains. Evidence of promising ion injection properties observed with cyclic voltammetry is complemented by strong electrochromism probed by spectroelectrochemistry. Blending these molecules with high molecular weight polyethylene oxide (PEO) is found to improve both ion injection and thin film stability. The molecules and their corresponding PEO blends are investigated as active layers in organic electrochemical transistors (OECTs). For the most promising molecule:polymer blend (P4E4:PEO), p‐type accumulation mode OECTs with µA drain currents, μS peak transconductances, and a µC* figure‐of‐merit value of 0.81 F V−1 cm−1 s−1 are obtained.

Molecular design strategies for high‐performance organic electrochemical transistors

“…There are only two cases of small molecules OECTs up to now. Nielsen and coworkers built two p-type small molecules using the benzene and EDOT units, named P2E2 and P4E4 33 (Figure 2A). To improve charge injection and overcome the low viscosity of small molecule solutions, they blended these molecules with high-molecular weight polyethylene oxide (PEO).…”

“…Different from OFET materials that only consider charge carrier mobility, both charge carrier (hole/ F I G U R E 2 Chemical structures of two small-molecule OECT materials: (A) P2E2 and P4E4, 33 (B) C60-TEG. 34 OECT, organic electrochemical transistor electron) transport and ion diffusion are important for a high-performance OECT material.…”

Conjugated molecules for colourimetric and fluorimetric sensing of sodium and potassium

“…While this proof-ofprinciple study was carried out with peripheral alkyl chains impairing good solubility and thus sensing behaviour in tetrahydrofuran and chloroform, recent work has demonstrated aqueous activity with p-conjugated molecules bearing ethylene glycol-based chains. 37 Further biological relevance can thus be sought through further synthetic design in particular through substituting the peripheral alkyl chains with more polar counterparts.…”

Fused Bithiophene Imide Dimer‐Based n‐Type Polymers for High‐Performance Organic Electrochemical Transistors

“…However, the development of n‐type (electron‐transporting) polymers lags greatly behind with the μC * values typically in the range of only 0.1–1 F cm −1 V −1 s −1 (Figure 1). [10, 22–25] The mismatch between n‐type and p‐type performance restricts the development of low‐power OECT‐based complementary circuits for on‐site amplification in bioelectronic applications [11, 26–28] . The poor n‐type OECT performance is mainly attributed to the low electron mobility since many high‐performance n‐type materials (poly(benzimidazobenzophenanthroline), BBL for instance) hold impressive C * of up to 900 F cm −3 , [29, 30] which is even larger than the high‐performance p‐type polymer analogues.…”