High‐Performance n‐Type Organic Electrochemical Transistors Enabled by Aqueous Solution Processing of Amphiphilicity‐Driven Polymer Assembly

Abstract

Despite the growing attention on organic electrochemical transistors (OECTs), most research has focused on the design of p-type active materials, and the number of high-performance n-type materials is limited. Herein, a series of naphthalene diimide-based polymers incorporated with asymmetrically branched oligo(ethylene glycol) (OEG) side chains are developed to enable green-solvent-processed, high-performance n-type OECTs. The branched OEG side chains afford sufficient solubility in eco-friendly ethanol/water solvent mixtures. Importantly, taking advantage of the amphiphilic nature of OEGbased polymers, ethanol/water solvents selectively solvate hydrophilic OEG side chains, while producing assembled π−π stacks of hydrophobic backbones. This enables highly ordered polymer packing with a preferential edge-on orientation, and thus excellent lateral charge transport. In particular, the fine-tuned OEG side chains of P(NDIMTEG-T) provide compact backbone packing, effective polaron generation, and superior electrochemical stability with optimized swelling capability. The resultant n-type OECT shows the best electrical/ electrochemical performance in the family, represented by a high transconductance (g m ) of 0.38 S cm −1 and a large figure-of-merit (µC*) of 0.56 F V −1 cm −1 s −1 .This study demonstrates the use of aqueous processing in OECTs, for the first time, and suggests important guidelines for the design of n-type organic mixed ionic-electronic conductors with excellent OECT characteristics.

Cyano‐Functionalized n‐Type Polymer with High Electron Mobility for High‐Performance Organic Electrochemical Transistors

“…The OECT devices of both polymers showed clear n-type accumulation-mode characteristics with almost negligible hysteresis in their transfer and output curves regardless of device gate voltage scan rate (Figures 3a-d, Table 2; with literature-reported channel materials for n-type OECTs; [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] please note the representative high-performance materials based on various electrondeficient building blocks are shown in color with displayed legends while the rest are shown in black.…”

“…This is also the first report of μ e,OECT > 0.1 cm 2 V −1 s −1 in n-type OECTs. [38][39][40][41][42][43][44][46][47][48]52] Meanwhile, the non-cyanated polymer f-BTI2g-TVT shows a much lower but still good μ e,OECT of 0.014 cm 2 V −1 s −1 , μC* of 1.50 F cm −1 V −1 s −1 , and g m,norm of 0.27 S cm −1 in n-type OECTs.…”

“…Since the pioneering work of p(gNDI-gT2) in 2016, [38] there are only limited number of reports on n-type materials for OECTs (please see summary in Table S1, Supporting Information). They mainly include donor-acceptor (D-A) polymers such as naphthalene diimde (NDI)-based P90, [39,40] p(C6-gNDI-gT2), [41] P(NDIMTEG-T), [42] P(C6-T2), [43] bithiophene diimide-based f-BTI2TEG-FT, [44] isoindigo-based AIG-BT, [45] lactone-based p(C-T), [46] and diketopyrrolopyrrolebased P(gPzDPP-CT2), [47] all-acceptor (A-A) ladder-type polymers BBL [48,49] and PgNaN, [50] small molecule C60-TEG. [51] n-Type organic mixed ionic-electronic conductors (OMIECs) with high electron mobility are scarce and highly challenging to develop.…”

“…[46] Therefore, it is highly challenging to simultaneously yield high electron mobility and ion transport capability to improve the μC* for n-type polymers. In order to improve μ e,OECT , various strategies have been employed such as side-chain engineering and backbone structure optimization, [41][42][43][44]46,47] increasing polymer molecular weight, [48] lowering device contact resistance. [58] To this end, utilizing the rich library of electrondeficient building blocks, which have been successful in building a great number of high mobility n-type polymers for organic thin-film transistors (OTFTs), [59][60][61][62] is considered as an effective approach to construct n-type OECT materials.…”

“…Their V g -dependent transconductance performances were also shown. e) Comparison of the μC* and μ e,OECT values of f-BTI2g-TVT/f-BTI2g-TVTCN polymerswith literature-reported channel materials for n-type OECTs;[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] please note the representative high-performance materials based on various electrondeficient building blocks are shown in color with displayed legends while the rest are shown in black.…”