Enhancing the Electrochemical Doping Efficiency in Diketopyrrolopyrrole‐Based Polymer for Organic Electrochemical Transistors

Abstract

The increasing interest in organic electrochemical transistors (OECTs) for next‐generation bioelectronic applications motivates the design of novel conjugated polymers with good electronic and ionic transport. Many conjugated polymers developed for organic field‐effect transistors (OFETs) exhibit high charge carrier mobilities but they are not suitable for OECTs due to poor ion‐uptake arising from the non polar alkyl chain substituted on the conjugated backbone. They are also sensitive to moisture, resulting in poor performance in aqueous electrolytes. Herein, the widely used conjugated building block diketopyrrolopyrrole (DPP) is used and functionalized it with polar triethylene glycol side chains (PTDPP‐DT) to promote ion penetration. The electrical performance of PTDPP‐DT based OECT in two types of aqueous electrolytes is studied and the electrochemical doping response is investivated. It is found that the tetrafluoroborate (BF4−) anion with large crystallographic radius allows high‐efficiency electrochemical doping of the PTDPP‐DT polymer, and thus gives rise to the high transconductance of 21.4 ± 4.8 mS with good device stability, where it maintained over 91 % of its doped‐state drain current after over 500 cycles of pulse measurement.

The effect of the donor moiety of DPP based polymers on the performance of organic electrochemical transistors

“…[34][35][36][37] Importantly, the top OECT performer in this work showed a lower threshold voltage (V TH = À0.36 V) than those of the previously reported D-A polymers, such as p(gDPP-T2) (V TH = À0.52 V) and PDPP-DT (V TH = À0.59 V) (Table S1, ESI †). 37,49 When we recorded the transient behaviour of these devices, we found a response time of around 7.3 ms and 8.7 ms for TDPP-gTVT and TDPP-gTBTT, respectively (Fig. S8a and b, ESI †), indicating that the TVT variant has a faster response than TBTT.…”

Molecular design strategies for high‐performance organic electrochemical transistors

“…In addition, other DPP-based polymers with different donors and side chains are studied. 66,67 Because it is difficult to lower the LUMO energy levels to achieve electron transport and maintain air stability, high-performance n-type conjugated polymers are very rare. Moreover, the existence of electrolyte (most commonly NaCl solution) aggravates the instability of polymers and makes the development of n-type OECTs F I G U R E 6 Chemical structures of the p-type third-generation semiconducting polymers for OECTs.…”

“…65 (E) DPP-based polymers. 36,39,66,67 DPP, diketopyrrolopyrrolep; IID, Isoindigo; OECTs, organic electrochemical transistors; PyDPP, pyridine-flanked DPP troublesome. The lack of n-type polymers whose performances can be comparable to p-type restricts the development of complementary logic circuits, which are the basis of flexible electronics.…”

Ionic‐Liquid Induced Morphology Tuning of PEDOT:PSS for High‐Performance Organic Electrochemical Transistors

“…[12,16] Nonetheless, a film of PEDOT:PSS is especially complex due to its heterogeneous nature consisting of the blend of two ionomers, giving rise to inherent disordered structures and poor interconnectivity within the conducting PEDOT-rich domains as compared to the homogeneous singlecomponent conjugated polymers. [17][18][19][20][21] Several efforts using various additives such as ethylene glycol (EG), Triton X-100, dimethyl sulfoxide, and sorbitol, [22][23][24] post-treatment with acids or bases, [11] and strain-engineering via uniaxial tension in fiber form [25] have been made to improve the electrical properties of PEDOT:PSS through the rearrangement of PEDOT:PSS chain conformation, or removal of excess PSS chains, building larger and more internally connected PEDOT-rich structures or inducing anisotropic crystallite orientation in PEDOT:PSS domains to facilitate charge transport. [10,[24][25][26][27][28][29] Among them, the additive ethylene glycol (EG) is the most commonly used, where the incorporation of EG facilitates the aggregation of PEDOT phase into larger PEDOT-rich domains with shorter π-π stacking.…”