Donor Functionalization Tuning the N‐Type Performance of Donor–Acceptor Copolymers for Aqueous‐Based Electrochemical Devices

Abstract

In this work, three n‐type donor–acceptor copolymers consisting of glycolated naphthalene tetracarboxylicdiimide (gNDI) coupled with variable donating companion moieties are reported. Using 2,2′‐bis(3,4‐ethylenedioxy)bithiophene, 2,​2′‐​bithiophene, 3,3′‐difluoro‐2,2′‐bithiophene (FBT), the donating strength of the donor units is systematically functionalized. These copolymers are used as a platform for aqueous‐based electrochemical devices, including energy‐storage devices, electrochromic devices (ECDs), and organic electrochemical transistors (OECTs). It is found that the electrochemical redox stability and electron mobility of copolymers are significantly improved via weakening the electron‐donating strength of donor units. gNDI coupling with FBT (gNDI‐FBT) exhibits a charge‐storage capacity exceeding 190 Fg−1, which is the highest value reported to date for NDI‐based polymer electrodes in aqueous media. For ECDs, gNDI‐FBT remains 100% of initial electrochromism contrast (∆%T = 20%) up to 1200 s. In addition, gNDI‐FBT outperforms its two analogs in OECTs, including lower threshold voltage (0.19 V), faster response time (45.5 ms), and higher volumetric capacitance (197 F cm−3). Moreover, gNDI‐FBT with fluorine atoms leads to the bipolarons delocalization along the polymer backbone and favorable molecular packing for ion–electron transport. Through such weak donor functionalization strategy, this work provides ways for n‐type copolymers tuning to access desirable performance metrics in optical, electrochemical, and bioelectronic applications.

n-Type Organic Electrochemical Transistors with High Transconductance and Stability

“…We calculated from the in-plane (100) peak, and the lamellar d-spacing is more than 3 Å narrower for the fluorinated gAIID-2FT (17.69 Å) compared to that for gAIID-T (21.65 Å), indicating that the fluorine atoms promote stronger intermolecular interactions with denser packing in the lamellar direction. The fluorine substitution results in a slight effect on the π–π spacing but enhances the lamellar packing, correlating well with the reported literature. ,, Another feature is the weak out-of-plane lamellar stacking peak ascribed to (200) of gAIID-2FT . We did not observe this peak for gAIID-T , suggesting that the fluorine promotes stronger molecular stacking.…”

“…The fluorine substitution results in a slight effect on the π−π spacing but enhances the lamellar packing, correlating well with the reported literature. 41,44,45 Another feature is the weak out-of-plane lamellar stacking peak ascribed to (200) of gAIID-2FT. We did not observe this peak for gAIID-T, suggesting that the fluorine promotes stronger molecular stacking.…”

Switching p-type to high-performance n-type organic electrochemical transistors via doped state engineering

“…To build complementary logic circuits for realizing high sensitivity and multiple device functions, n-type OECTs with comparable performance are necessary 6 – 8 . Unfortunately, compared to p-type ones, n-type OECT materials lag far behind in terms of both quantity and device performance, with μC * usually less than 1 F cm −1 V −1 s −1 and τ on / τ off over 10 ms 9 – 16 .…”

“…In the development of n-type organic field-effect transistor (OFET) materials, researchers usually introduce more electron-deficient moieties to lower the lowest unoccupied molecular orbital (LUMO) energy level. This “lowering LUMO” strategy effectively enhances electron mobility and has promoted the fast development of n-type OFETs 16 – 24 . Inspired by this strategy, in the last 3 years, several strong electron-deficient n-type building blocks have been designed and used for OECTs, including naphthalene diimide (NDI) 9 , 11 , 25 , benzodifurandione-based oligo( p -phenylene vinylene) (BDOPV) 26 , bithiophene imide (BTI) 27 , 28 , pyrazine-flanked diketopyrrolopyrrole (PzDPP) 11 , 7,7′-diazaisoindigo (AIG) 29 , and some ladder-type polymers 15 , 30 .…”

Donor Engineering Tuning the Analog Switching Range and Operational Stability of Organic Synaptic Transistors for Neuromorphic Systems

“…Donor engineering has been a versatile strategy to tune the energy levels, molecular conformation and aggregation, as well as the charge transport properties of conjugated polymers in the field of organic electronic. [ 32 ] Rational donor unit design can also optimize the carrier mobility, [ 33 ] redox stability, [ 34 ] and ion uptake properties of conjugated polymers. [ 35 ] For example, 3,4‐alkylenedioxythiophene (XDOT)‐based electron‐rich polymers have several distinct advantages over thiophene analogues.…”