Skip to main content
NCBI home page
Polymer Science & Technology logoLink to Polymer Science & Technology
. 2026 Apr 24;2(6):419–428. doi: 10.1021/polymscitech.6c00036

Cross-Conjugated Donor–Acceptor Polymers for High-Performance Organic Electrochemical Transistors

Sijing Wang †,‡, Yidan Luan †,‡, Feng Ye †, Riqing Ding †, Jiaqiang Liao †,‡, Rongsheng Zhang †,‡, Shuo Chen †,‡, Lei Fang †,*, Zi-Hao Guo †,‡,*
PMCID: PMC13295191  PMID: 42368471

Abstract

The development of high-performance polymer mixed ionic–electronic conductors (PMIECs) is critical for advancing organic electrochemical transistors (OECTs). While the field has been dominated by linearly conjugated polymers, cross-conjugated systems represent a vast and largely unexplored materials platform. Their distinctive optical, electronic, and tailorable redox characteristics endow them with considerable, yet underutilized, potential for the development of a range of OECT applications. In this work, we designed and synthesized two donor–acceptor (D–A) polymers, P­(TIDPg-TVT) and P­(TIDPg-CNTVT), based on a planar, hydrogen-bond-locked cross-conjugated acceptor (TIDP). P­(TIDPg-TVT) exhibited n-type-dominant ambipolar transport coupled with high operational stability, achieving an n-type μC* of 3.25 F cm–1 V–1 s–1. The cyanofunctionalized polymer P­(TIDPg-CNTVT) displayed pronounced n-type characteristics, achieving a high μC* of 4.93 F cm–1 V–1 s–1 along with efficient doping. Leveraging these polymers as the active layer, complementary OECT inverters were fabricated and demonstrated high voltage gains. This work successfully validates cross-conjugation as a versatile design paradigm for high-performance PMIECs, thereby providing a molecular engineering strategy to realize balanced ionic and electronic transport, which is critical for the development of high-performance organic bioelectronic devices.

Keywords: cross-conjugated, polymer mixed ionic–electronic conductors, conjugated polymer, organic electrochemical transistors, n-type polymer semiconductors

graphic file with name ps6c00036_0008.jpg

graphic file with name ps6c00036_0006.jpg

Introduction

Organic electrochemical transistors (OECTs) have emerged as a transformative technology for bridging the gap between biological systems and electronic devices, enabling applications ranging from biosensing and neuromorphic computing to wearable healthcare. − Unlike conventional field-effect transistors, where charge transport is confined to a semiconductor–dielectric interface, − OECTs operate via volumetric electrochemical doping: an applied gate voltage drives ions from an electrolyte into the bulk of a polymeric channel material, doping it throughout its volume and modulating its conductivity. − This unique operating mechanism relies on polymer mixed ionic–electronic conductors (PMIECs) as the channel material, which must support both ionic and electronic transport. − This fundamental operating principle establishes the μC* product, , combining charge carrier mobility (μ) and volumetric capacitance (C*), as the critical performance parameter for evaluating PMIECs. Consequently, the strategic molecular design of polymers that can optimally balance efficient electronic transport with rapid ion penetration is therefore paramount for advancing OECT performance. ,

Notably, the molecular design of high-performance semiconducting polymers for OECTs has been predominantly guided by the paradigm of linear conjugation, , which ensures continuous pathways for efficient electron delocalization and charge transport. In contrast, cross-conjugated structures, systems featuring branched π-electron systems that interrupt direct conjugation along the backbone, constitute a vast and relatively unexplored chemical space. Conventional wisdom posits that such structural interruptions inherently hinder long-range charge transport. However, a series of fundamental studies have revealed that the electronic structure of cross-conjugated systems can be dynamically modulated by electrochemical stimuli. , For instance, the sp3-hybridized nitrogen in cross-conjugated arylamines can be oxidized to an sp2 state, dynamically forging a linear conjugation bridge. Similarly, ketone-based cross-conjugated units undergo reductive activation that extends effective conjugation. , This property establishes an inherent consistency with the operational principle of the OECTs, which fundamentally rely on electrochemical doping. Coupled with the unique optical, electronic, and redox behaviors arising from their branched π-delocalization, cross-conjugated polymers thus represent a distinctive, promising, and vastly unexplored platform for the development of PMIECs. Given this potential, a direct investigation into the structure–property relationships within such frameworks is crucial to advancing the design of the OECT materials and assessing their practical viability.

To validate the potential of cross-conjugated systems for OECTs, we selected the building block TIDP as a model acceptor, which is based on a cross-conjugated 2,5-dimethylene-3,6-diketopiperazine (DMDKP) core containing two amide groups. Its hydrogen-bond-locked planar structure supports effective π-electron delocalization within the cross-conjugated framework, while its strong electron-deficient character provides a versatile platform for tuning electronic properties via donor pairing. However, exploiting this distinctive molecular architecture for high-performance PMIECs requires a fundamental understanding and optimization of the intricate balance between electronic transport and ion permeation within the polymer backbone. This demands meticulous control over not only electronic affinity but also the material microstructure, hydrophilicity, and electrochemical doping properties.

Herein, we present the design and synthesis of two novel donor–acceptor (D–A) polymers based on the cross-conjugated TIDP building block, namely, P­(TIDPg-TVT) and P­(TIDPg-CNTVT). We systematically tuned the electronic character of the donor unit to investigate how this cross-conjugated scaffold can be engineered to balance μ, C*, and operational stability, which are all critical determinants of the OECT performance. Both polymers feature oligoethylene glycol (OEG) side chains to ensure ion permeability and solution processability. − The donor unit was strategically modified by introducing two electron-withdrawing cyano groups, transforming the TVT (1,2-di­(thiophen-2-yl)­ethene) unit into CNTVT (1,2-bis(3-cyanothiophene-2-yl)­ethene) to tune the polymer structure and device properties. The polymers were comprehensively characterized with regard to their optical, electrochemical, and morphological properties. Crucially, P­(TIDPg-TVT) exhibited n-type-dominant ambipolar transport, achieving a high n-type μC* of 3.25 F cm–1 V–1 s–1 alongside exceptional operational stability (97% current retention after 2000 rapid switch cycles). In contrast, P­(TIDPg-CNTVT) displayed purely n-type characteristics featuring a higher μC* of 4.93 F cm–1 V–1 s–1, a lower doping threshold, and a higher C*. Specifically, cyanofunctionalization lowered the LUMO level for improved n-type conductivity, while also fostering a microstructure that facilitates rapid ion uptake and high volumetric capacitance. Their application potential was further demonstrated in logic circuits, where both single-material ambipolar and typical complementary inverters achieved a high voltage gain. This work establishes cross-conjugation as a viable and versatile strategy for designing high-performance PMIECs, offering a new avenue toward optimizing ionic-electronic coupling in organic bioelectronics.

Results and Discussion

The synthetic routes to both polymers P­(TIDPg-TVT) and P­(TIDPg-CNTVT) are depicted in Figure a and the synthetic details can be found in the Supporting Information. TPDg was prepared according to the published protocol, but with modifications suitable for oligoethylene glycol functionalization to facilitate ion transport and ensure solution processability of the polymers. A triethylamine (TEA) catalyzed Knoevenagel condensation of TPDg with 1,4-diacetylpiperazine-2,5-dione successfully afforded TIDPg. TIDPg was subsequently dibrominated using NBS to yield the key monomer TIDPg-2Br. Finally, TIDPg-2Br was copolymerized with distannylated comonomers TVT-2Sn and CNTVT-2Sn via Stille cross-coupling polymerization, producing target polymers P­(TIDPg-TVT) and P­(TIDPg-CNTVT), respectively. Polymer purification was performed by sequential Soxhlet extraction using methanol, hexane, acetone, and chloroform (CF) to remove impurities and low-molecular-weight oligomers. The high-molecular-weight fractions were subsequently obtained in the final hexafluoroisopropyl alcohol (HFIP) eluent. These fractions were then dissolved in HFIP, reprecipitated into cold methanol, collected by filtration, and dried under a vacuum. The molecular weights and distributions of the purified polymers were determined by gel permeation chromatography (GPC) using HFIP as the eluent (Figure S7), with the results summarized in Table . Thermogravimetric analysis (TGA) revealed that both polymers exhibit high thermal stability, with 5% weight loss temperatures (T d) exceeding 400 °C (Figure S8).

1.

1

Open in a new tab

(a) Synthetic route to the polymers P­(TIDPg-TVT) and P­(TIDPg-CNTVT). Reaction conditions: (i) NaH, DMF, 0 °C to room temperature (RT); (ii) TFA, CF, RT; (iii) oxalyl dichloride, TEA, DCM, 0 °C to RT; (iv) 1,4-diacetylpiperazine-2,5-dione, TEA, CF, DMF, RT; (v) NBS, THF, 0 °C to RT; (vi) Pd2(dba)3, P­(o-Tol)3, toluene, 140 °C. (b) The optimized molecular geometry and Frontier molecular orbitals using DFT calculations at B3LYP/6-311G­(d,p) level.

1. Optical and Electrochemical Properties of the Polymers.

polymer M n[kDa]/D̵ λmax soln [nm] λmax film [nm] λonset (nm) E g opt [nm] E LUMO [eV] E HOMO [eV] E g cv [eV]
P(TIDPg-TVT) 19.2/2.1 910 918 1041 1.19 –3.90 –4.86 0.96
P(TIDPg-CNTVT) 15.1/2.5 760 851 982 1.26 –4.08 –5.09 1.01
Open in a new tab
a

Maximum absorption peak in solution (HFIP).

b

Maximum absorption peak in the thin film.

c

The onset of film absorption.

d

Optical band gap calculated by E g opt = 1240/λonset film.

e

Estimated from CV measurements using the equation. E LUMO = −(4.80 + E onset red).

f

E HOMO = −(4.80 + E onset ox).

g

E g cv was calculated by the equation, E g cv = E LUMO–E HOMO.

For deep insight into the electronic properties and geometric configurations of polymers, DFT calculations were conducted at the B3LYP/6-311G (d,p) level using a trimer model. To simplify the calculations, all of the OEG side chains were replaced with methyl groups. The optimized molecular geometries (Figure b) showed that for P­(TIDPg-TVT), the dihedral angles between the ethylene and the thiophene linked to TIDP and between TIDP and TVT were 1.2° and 9.7°, respectively. Upon introduction of electron-withdrawing cyano groups to form P­(TIDPg-CNTVT), the corresponding dihedral angles increased to 3.2° and 13.8°, respectively. The resulting larger twist angles are typically considered detrimental to interchain π–π stacking and long-range charge transport. However, for OECTs, such a conformational change may facilitate ion penetration and electrochemical doping. Additionally, the calculated HOMO and LUMO levels of P­(TIDPg-TVT) and P­(TIDPg-CNTVT) were −4.86/–3.33 eV and −5.34/–3.67 eV (Figure b), respectively. The introduction of cyano groups in P­(TIDPg-CNTVT) significantly lowered both the Frontier molecular orbital (FMO) level. The FMO distributions of the two polymers differ markedly. For P­(TIDPg-TVT), the HOMO is primarily delocalized over the donor unit, while the LUMO is strongly localized on the acceptor (TIDP) unit. In contrast, for P­(TIDPg-CNTVT), both the HOMO and LUMO become spatially segregated in the polymer backbone. This distinct orbital localization pattern originates from the markedly diminished electron-donating ability of the cyanated donor, , which thereby accounts for the material’s transition to purely n-type transport.

The optical properties of both polymers were investigated by UV–vis–NIR absorption spectroscopy in a dilute solution and as thin films (Figure a). The corresponding absorption parameters are summarized in Table . In dilute solution, both polymers exhibit a pronounced intramolecular charge-transfer (ICT) absorption band between 600 and 1200 nm, which originates from the interaction between the TIDPg acceptor and the donor co-units. The maximum absorption peaks (λmax soln) of P­(TIDPg-TVT) and P­(TIDPg-CNTVT) in dilute solution are located at 910 and 760 nm, respectively. This significant blueshift of ≈150 nm for P­(TIDPg-CNTVT) is attributed to the introduction of cyano groups on the donor unit, which reduces the donor strength and consequently weakens the intramolecular D–A character, coupled with increased backbone torsion that affects the conjugation along the polymer chain. From solution to thin films, both polymers displayed more pronounced vibronic features including well-resolved 0–0 and 0–1 vibrational peaks. This suggests good backbone rigidity and planarity, which facilitate intermolecular ordering and are beneficial for charge transport. , Furthermore, the absorption maximum of P­(TIDPg-CNTVT) shows a typical redshift of ≈8 nm in the film, while that of P­(TIDPg-TVT) exhibits a pronounced blueshift of ≈91 nm, which is likely due to intermolecular H-aggregation dominating over the solution-to-solid planarization effect. Cyclic voltammetry (CV) measurements were performed on thin films to determine the electrochemical energy levels of both polymers using ferrocene/ferrocenium (Fc/Fc+) as an internal reference. As shown in Figure b, reversible oxidation and reduction waves were observed for both materials in acetonitrile containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6). The HOMO and LUMO energy levels were determined to be −4.86 and −3.90 eV for P­(TIDPg-TVT) and −5.09 and −4.08 eV for P­(TIDPg-CNTVT), respectively. The results are in good agreement with the values obtained from the DFT calculations. The lower-lying LUMO levels of P­(TIDPg-CNTVT) facilitate electron injection, promoting n-type operation in OECT devices. Accordingly, the electrochemical bandgaps are calculated to be 0.96 and 1.01 eV, respectively, in good agreement with the trend from optical absorption.

2.

2

Open in a new tab

(a) UV–vis–NIR absorption spectra of (a) P­(TIDPg-TVT) and P­(TIDPg-CNTVT). (b) Thin-film cyclic voltammograms of P­(TIDPg-TVT) and P­(TIDPg-CNTVT). UV–vis–NIR electrochemical absorption spectra of (c) P­(TIDPg-TVT) and (f) P­(TIDPg-CNTVT) thin films in a 0.1 M NaCl electrolyte. Cyclic voltammetry scan of the polymer films in a 0.1 M NaCl aqueous solution: (d) P­(TIDPg-TVT) and (e) P­(TIDPg-CNTVT). Water droplet contact image on the film surface of (g) P­(TIDPg-TVT) and (h) P­(TIDPg-CNTVT). (i) Absolute change of neutral polymer ICT peaks and polarons peak under applied bias.

The electrochemical properties of polymers in aqueous media of a 0.1 M NaCl solution were investigated by using CV and UV–vis–NIR spectroelectrochemistry. As shown in Figure d,e, P­(TIDPg-TVT) and P­(TIDPg-CNTVT) display pronounced and reversible reductive events with a good cycling stability over 200 cycles within a potential window of 0 to −0.7 V vs. Ag/AgCl reference. The onsets of reduction in aqueous media are −0.22 and −0.41 V for P­(TIDPg-TVT) and P­(TIDPg-CNTVT), respectively, which follows the same trend as that observed in the TBAPF6 electrolyte. This potential shift between organic and aqueous media stems from differences in both the charge-compensating cations (their density and size) and the interactions between the PMIECs and the electrolyte solvents. The ionic doping characteristics of two polymers were further investigated by UV–vis–NIR spectroelectrochemistry. Both polymers exhibited distinct electrochromic behavior as the applied potential was stepped from 0 to −1.0 V vs Ag/AgCl in 0.1 V increments (Figure c,f). P­(TIDPg-TVT) exhibited a slight reduction of the absorption with increased absorbance at the longer wavelengths due to a polaronic (and/or bipolaronic) absorption. In contrast, the ICT absorption of P­(TIDPg-CNTVT) was almost completely bleached, accompanied by the appearance of a strong polaronic absorption band at long wavelengths in the range of 1100–1300 nm, indicative of a higher electrochemical doping efficiency than P­(TIDPg-TVT). The integrals of the ICT and polaron absorption bands were plotted versus the applied voltage (Figure i). For P­(TIDPg-TVT), the ICT absorption began to diminish at −0.5 V, whereas that of P­(TIDPg-CNTVT) underwent a more pronounced and rapid decline starting at a more positive potential of −0.3 V, confirming its greater ease of doping. This lower doping threshold and higher efficiency are attributed not only to its deeper-lying LUMO level but also to its stronger ion-uptake ability as seen from the electrochemical impedance spectroscopy (EIS). Water contact angle measurements also showed that the P­(TIDPg-CNTVT) film was more hydrophilic (θ ≈ 53°) than the P­(TIDPg-TVT) film (θ ≈ 60°) (Figure g,h), which is essential for efficient ion uptake and electrochemical doping in an aqueous environment.

OECT devices were fabricated to evaluate the electrical performance of the two polymer active layers. The devices, featuring a channel width/length (W/L) of 100/10 μm, were patterned via photolithography and parylene deposition. The OECT devices were tested in a 0.1 M NaCl solution using Ag/AgCl as the gate electrode (the details are included in Supporting Information). The performance of device is evaluated based on eq derived from the Bernard model.

gm=WdLμC*(Vg−Vth) 1

where W, L, and d represent the channel width, length, and film thickness, respectively, V th is the threshold voltage, and V g is the applied voltage. The transfer and output characteristics of both polymer-based OECTs are shown in Figure , and the corresponding OECT data are summarized in Table . P­(TIDPg-TVT) exhibits ambipolar charge transport, which is dominated by n-type operation owing to the relatively unstable p-type doping state, whereas P­(TIDPg-CNTVT) displays purely n-type operation. For both devices, the drain current increases with gate voltage, indicating that they operate in accumulation mode. Polymer P­(TIDPg-TVT) yielded a maximum μC* of 3.25 F cm–1 V–1 s–1 at V g = 0.84 V with a V th of 0.58 V, corresponding to a high geometry-normalized transconductance (g m,nrom.) of 0.83 S cm–1. For P­(TIDPg-CNTVT), its OECT devices displayed a lower V th of 0.48 V, consistent with the lower doping threshold revealed by spectroelectrochemistry. The maximum μC* and g m,norm. of P­(TIDPg-CNTVT) are calculated to be 4.93 F cm–1 V–1 s–1 and 0.82 S cm–1 at V g = 0.65 V, respectively. Moreover, the P­(TIDPg-TVT)- and P­(TIDPg-CNTVT)-based OECTs exhibit similar high I on/I off ratio values of >106. These results demonstrate that TIDP-based cross-conjugated polymers achieve outstanding mixed ionic-electronic transport, thus enabling highly efficient signal transduction and amplification in OECT devices. EIS was employed to extract C* (Figure S10). P­(TIDPg-CNTVT) exhibited a significantly higher C* of 293 F cm–3 than P­(TIDPg-TVT) (233 F cm–3), an enhancement that we attribute to stronger ion-uptake ability, in line with its higher hydrophilicity demonstrated via contact angle measurements. Accordingly, the OECT electron mobilities (μe,OECT) of P­(TIDPg-TVT) and P­(TIDPg-CNTVT) were further characterized and are summarized in Table .

3.

3

Open in a new tab

(a) A schematic of the OECT gated by a 0.1 M NaCl aqueous electrolyte. (b) n-type transfer and (c) output curves of the P­(TIDPg-TVT)-based OECTs. (e) n-type transfer and (f) output curves of the P­(TIDPg-CNTVT)-based OECTs. Operational stability measurement of the OECTs based on (d) P­(TIDPg-TVT) and (g) P­(TIDPg-CNTVT). Device transient response measurement during pulse operation for (h) P­(TIDPg-TVT)-based OECTs and (i) P­(TIDPg-CNTVT)-based OECTs.

2. Summary of OECT Parameters for P­(TIDPg-TVT) and P­(TIDPg-CNTVT).

polymer g m,norm. [S cm–1] d [nm] C* [F cm–3] μC* [F cm–1 V–1 s–1] μe [F cm2 V–1 s–1] I on/off τon [ms] τoff [ms] type
P(TIDPg-TVT) 0.84 108 233 3.25 0.014 >106 6.72 5.71 n
P(TIDPg-CNTVT) 0.82 60.8 293 4.93 0.015 >106 5.27 7.91 n
Open in a new tab
a

The transconductance normalized by the channel geometry. The W/L of all the devices is 100/10 μm.

b

The thickness of the polymers film.

c

Measured by the electrochemical impedance spectroscopy and reported as the average values.

d

Extracted from the slope of g m as a function of (Wd/L) (V th–V g).

e

Calculated from the value of μC* and C*.

The operational stability and response times are of great importance for practical applications. The OECT device based on P­(TIDPg-TVT) showed a significantly higher current retention of 97% after 2000 switching cycles (1000 s) measurement in air, whereas the P­(TIDPg-CNTVT)-based device lost nearly half of its current (57% retention) after only 1000 cycles (Figure d,g). The superior operational stability of P­(TIDPg-TVT) is attributed not only to its more ordered molecular packing but also to its relatively moderate ion uptake behavior. In contrast, the lower stability of P­(TIDPg-CNTVT) is likely related to its stronger ion uptake and higher volumetric capacitance, which can induce a more pronounced swelling during repeated cycling. The response time was extracted by the exponential fit to the I d curve, which afforded on/off time constants (τon/τoff) of 6.72/5.71 ms for P­(TIDPg-TVT) and 5.27/7.91 ms for P­(TIDPg-CNTVT), respectively (Figure h,i). In brief, our TIDP-based cross-conjugated polymers enable high-performance OECTs exhibiting key merits, such as a high μC* product, exceptional operational stability, and a fast response speed.

Complementary inverters for biosignal amplification are typically built by integrating discrete p-type and n-type OECTs. To evaluate the potential of our materials in such systems, we fabricated a complementary inverter by combining the n-type polymer P­(TIDPg-CNTVT) with a high-performance p-type polymer P­(g42T-T) (Figure ). The voltage transfer characteristics of the complementary inverter with various supply voltages (V DD) are displayed in Figure S11. With a gradually increasing input voltage, the pull-up channel switches from an “ON” to an “OFF” state, whereas the pull-down channel is the opposite. A maximum voltage gain of 27.1 V/V was achieved at V DD = 0.8 V (Figure ). However, the switching threshold deviated significantly from the ideal V DD/2, indicating an imbalance in the driving strengths of the p- and n-type channels. This imbalance could stem from several factors, such as a mismatch in the V th between the two materials or differences in their charge carrier mobilities, highlighting the critical need for developing high-performance n-type PMIECs and electron-deficient building blocks to achieve truly balanced and high-gain complementary circuits. Notably, the ambipolar character of P­(TIDPg-TVT) offers an alternative, simplified circuit architecture. We constructed an inverter using two identical P­(TIDPg-TVT) transistors (Figure S12). This configuration yielded a high gain of 26.3 V/V at V DD = 0.9 V, demonstrating the feasibility of simplified, symmetric circuitry based on a single ambipolar P­(TIDPg-TVT) material. These results collectively underscore the versatility and high performance of our cross-conjugated polymers, thereby demonstrating the potential of this molecular design strategy for organic electronic devices.

4.

4

Open in a new tab

(a) Circuit configuration of the complementary inverter. (b) Voltage output curves of the complementary inverter and (c) the associated voltage gains at various supply voltages.

To further explore the relationship between device performance and polymer structure, thin film morphologies and microstructures were analyzed by using grazing incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM). Figure shows the two-dimensional (2D)-GIWAXS patterns and corresponding one-dimensional (1D) line-cut profiles of two polymers. The correlation parameters of polymer films (π–π stacking and lamellar stacking) are summarized in Table S3. Detailed line-cut analysis showed that polymer P­(TIDPg-TVT) tends to form an ordered edge-on packing texture, exhibiting lamellar diffraction peaks extending up to third order (300) along the out-of-plane (OOP) direction with a strong (010) π–π diffraction peak in the in-plane (IP) direction. The π–π and lamellar stacking distances of P­(TIDPg-TVT) were calculated to be 3.31 and 19.18 Å, respectively. For P­(TIDPg-CNTVT), both IP and OOP profiles presented strong lamellar diffraction peaks (Figure e), implying their mixed edge-on and face-on packing orientation and yielding π–π and lamellar stacking distances of 3.41 and 19.04 Å, respectively. We calculated the crystal coherence lengths (CCLs) for (100) and (010) according to the Scherrer equation. CCL xy,100 and CCL z,010 values of P­(TIDPg-TVT) are larger than those of P­(TIDPg-CNTVT). The stronger intermolecular π–π interactions and higher crystallinity of P­(TIDPg-TVT), which result from the uniform molecular alignment promoted by its higher planarity, collectively contribute to its enhanced device operational stability. AFM height images show that both polymer films have a smooth surface with a small root-mean-square (RMS) roughness (Figure c,f), with that of P­(TIDPg-CNTVT) being slightly higher than that of P­(TIDPg-TVT). In the context of OECTs, where operation relies on volumetric ion doping, the larger roughness of P­(TIDPg-CNTVT) implies larger voids that facilitate ion penetration, contributing to its higher volumetric capacitance.

5.

5

Open in a new tab

2D-GIWAXS images and corresponding 1D line cut profiles along the in-plane and out-of-plane directions for (a,b) P­(TIDPg-TVT) and (d,e) P­(TIDPg-CNTVT). AFM height images (5 × 5 μm) for (c) P­(TIDPg-TVT) and (f) P­(TIDPg-CNTVT) thin films.

Conclusion

In summary, we report the rational design and successful synthesis of two novel cross-conjugated donor–acceptor polymers, P­(TIDPg-TVT) and P­(TIDPg-CNTVT), which serve as high PMIECs for the development of OECTs. The cyano-functionalized P­(TIDPg-CNTVT) exhibits superior n-type charge transport performance, achieving a high μC* of 4.93 F cm–1 V–1 s–1 together with a low electrochemical doping threshold; this outstanding performance is attributed to its downshifted LUMO energy level and ion-accessible microstructural features that facilitate rapid ion uptake and efficient volumetric doping. In contrast, P­(TIDPg-TVT) demonstrates remarkable operational stability with 97% current retention after 2000 switching cycles, coupled with n-type-dominant ambipolar charge transport characteristics. The practical application potential of these cross-conjugated polymers is further validated in organic logic circuits: the complementary inverter based on P­(TIDPg-CNTVT) as the n-type component delivers a high voltage gain of 27.1 V/V, while a simplified single-material inverter constructed from P­(TIDPg-TVT) achieves a comparable gain of 26.3 V/V. Collectively, our findings establish cross-conjugation as a viable and versatile molecular design strategy for the development of high-performance PMIECs. This work not only unlocks the untapped potential of cross-conjugated systems for OECT applications but also provides a new molecular engineering paradigm to optimize the balance of ionic and electronic transport in organic mixed conductors, offering valuable insights into the rational design of advanced materials for next-generation organic bioelectronic devices.

Supplementary Material

ps6c00036_si_001.pdf (1.7MB, pdf)

Acknowledgments

This work is supported by the National Natural Science Foundation of China (Nos.22571096 and 22271101).

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/polymscitech.6c00036.

  • Additional experimental details, synthesis and characterizations, molecular weights, thermal properties, OECT measurements, electrochemical impedance spectroscopy, complementary inverter measurements, and 1H NMR and 13C NMR spectra (PDF)

§.

S. W. and Y. L. contributed equally to this work.

The authors declare no competing financial interest.

References

  1. Cea C., Spyropoulos G. D., Jastrzebska-Perfect P., Ferrero J. J., Gelinas J. N., Khodagholy D.. Enhancement-mode ion-based transistor as a comprehensive interface and real-time processing unit for in vivo electrophysiology. Nat. Mater. 2020;19(6):679–686. doi: 10.1038/s41563-020-0638-3. [DOI] [PubMed] [Google Scholar]
  2. Khodagholy D., Doublet T., Quilichini P., Gurfinkel M., Leleux P., Ghestem A., Ismailova E., Hervé T., Sanaur S., Bernard C., Malliaras G. G.. In vivo recordings of brain activity using organic transistors. Nat. Commun. 2013;4(1):1575. doi: 10.1038/ncomms2573. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Rivnay J., Inal S., Salleo A., Owens R. M., Berggren M., Malliaras G. G.. Organic electrochemical transistors. Nat. Rev. Mater. 2018;3(2):17086. doi: 10.1038/natrevmats.2017.86. [DOI] [Google Scholar]
  4. Van de Burgt Y., Lubberman E., Fuller E. J., Keene S. T., Faria G. C., Agarwal S., Marinella M. J., Alec Talin A., Salleo A.. A non-volatile organic electrochemical device as a low-voltage artificial synapse for neuromorphic computing. Nat. Mater. 2017;16(4):414–418. doi: 10.1038/nmat4856. [DOI] [PubMed] [Google Scholar]
  5. Amna B., Ozturk T.. Organic field-effect transistor-based sensors: recent progress, challenges and future outlook. J. Mater. Chem. C. 2025;13(17):8354–8424. doi: 10.1039/D4TC04265D. [DOI] [Google Scholar]
  6. Lei T., Dou J.-H., Cao X.-Y., Wang J.-Y., Pei J.. Electron-Deficient Poly­(p-phenylene vinylene) Provides Electron Mobility over 1 cm2 V–1 s–1 under Ambient Conditions. J. Am. Chem. Soc. 2013;135(33):12168–12171. doi: 10.1021/ja403624a. [DOI] [PubMed] [Google Scholar]
  7. Ye F., He X., Zhou F., Guo J.-C., Jiang L., Hu D., Guo Z.-H., Ma Y.. Revealing the “AABB/ABAB Sequential Isomeric Effect” on Diketopyrrolopyrrole-Based All-acceptor Semiconducting Polymers. ACS Appl. Polym. Mater. 2022;4(11):8656–8664. doi: 10.1021/acsapm.2c01584. [DOI] [Google Scholar]
  8. Zhang S., Liu Y., Dong H., Li Y., Zhang K., Xian K., Han Y., Ye L., Heeney M., Fei Z.. Isomeric 1,4-Dihydropentalene-Containing Building Blocks for High Mobility Ladder-Type Conjugated Polymers. Angew. Chem. Int. Ed. 2025;64(19):e202500860. doi: 10.1002/anie.202500860. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Zhang Y., Wang Y., Gao C., Ni Z., Zhang X., Hu W., Dong H.. Recent advances in n-type and ambipolar organic semiconductors and their multi-functional applications. Chem. Soc. Rev. 2023;52(4):1331–1381. doi: 10.1039/D2CS00720G. [DOI] [PubMed] [Google Scholar]
  10. Chen Z., Ding X., Wang J., Guo X., Shao S., Feng K.. π-Conjugated Polymers for High-Performance Organic Electrochemical Transistors: Molecular Design Strategies, Applications and Perspectives. Angew. Chem. Int. Ed. 2025;64(7):e202423013. doi: 10.1002/anie.202423013. [DOI] [PubMed] [Google Scholar]
  11. Dai H., Yue W. n-.. Type Organic Mixed Ionic-Electronic Conductors for Organic Electrochemical Transistors. Adv. Eng. Mater. 2024;26(9):2301860. doi: 10.1002/adem.202301860. [DOI] [Google Scholar]
  12. Lei Y., Li P., Zheng Y., Lei T.. Materials design and applications of n-type and ambipolar organic electrochemical transistors. Mater. Chem. Front. 2023;8(1):133–158. doi: 10.1039/D3QM00828B. [DOI] [Google Scholar]
  13. Wang Y., Wustoni S., Surgailis J., Zhong Y., Koklu A., Inal S.. Designing organic mixed conductors for electrochemical transistor applications. Nat. Rev. Mater. 2024;9(4):249–265. doi: 10.1038/s41578-024-00652-7. [DOI] [Google Scholar]
  14. Huang Z., Li P., Lei Y., Deng X.-Y., Chen Y.-N., Tian S., Pan X., Lei X., Song C., Zheng Y., Wang J.-Y., Zhang Z., Lei T.. Azonia-Naphthalene A Cationic Hydrophilic Building Block for Stable N-Type Organic Mixed Ionic-Electronic Conductors. Angew. Chem. Int. Ed. 2024;63(6):e202313260. doi: 10.1002/anie.202313260. [DOI] [PubMed] [Google Scholar]
  15. Kukhta N. A., Marks A., Luscombe C. K.. Molecular Design Strategies toward Improvement of Charge Injection and Ionic Conduction in Organic Mixed Ionic–Electronic Conductors for Organic Electrochemical Transistors. Chem. Rev. 2022;122(4):4325–4355. doi: 10.1021/acs.chemrev.1c00266. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Zhang C., Zheng Y., Li Y., Xue Z., Zhu X., Chen J., Ma J., Zhang Z., Zhong H., Yue W., Lei T., Fei Z.. Polythiophenes for High-Performance N-type Organic Electrochemical Transistors. Adv. Funct. Mater. 2025;35(23):2419706. doi: 10.1002/adfm.202419706. [DOI] [Google Scholar]
  17. Jiang X., Wang Q., Wang Z., Dong B., Huang L., Chi L.. Recent Progresses on the High Performance Organic Electrochemical Transistors. Chem. Res. Chin. Univ. 2021;37(5):975–988. doi: 10.1007/s40242-021-1306-0. [DOI] [Google Scholar]
  18. Wang Y., Tan J., Hou H., Maricherla H., Ravva M. K., Zhu X., Liu R., He J., Lin Y., McCulloch I., Li Z., Yue W.. High Performing Ambipolar Organic Electrochemical Transistors and Solid-State Inverters Enabled by Hydrophilic/Hydrophobic Side Chains Integration. Adv. Mater. 2026;38:e15186. doi: 10.1002/adma.202515186. [DOI] [PubMed] [Google Scholar]
  19. Yu S., Wu H.-Y., Lemaur V., Kousseff C. J., Beljonne D., Fabiano S., Nielsen C. B.. Cation-Dependent Mixed Ionic-Electronic Transport in a Perylenediimide Small-Molecule Semiconductor. Angew. Chem. Int. Ed. 2024;63(42):e202410626. doi: 10.1002/anie.202410626. [DOI] [PubMed] [Google Scholar]
  20. Duan J., Ding J., Wang D., Zhu X., Chen J., Zhu G., Chen C., Yu Y., Liao H., Li Z., Di C.-a., Yue W.. Enhancing the Performance of N-Type Thermoelectric Devices via Tuning the Crystallinity of Small Molecule Semiconductors. Adv. Sci. 2023;10(3):2204872. doi: 10.1002/advs.202204872. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Ding R., Zhang X., Luan Y., Peng M., Chen W., Wang S., Su S., Lu S., Jeong S. Y., Woo H. Y., Guo X., Feng K., Guo Z.-H.. Donor Engineering for High Performance n-Type OECT Materials with Exceptional Operational Stability. Angew. Chem. Int. Ed. 2025;64(36):e202513182. doi: 10.1002/anie.202513182. [DOI] [PubMed] [Google Scholar]
  22. Yang W., Ma S., Gámez-Valenzuela S., Jeong S. Y., Lee J.-W., Cai H., Zhu R., Liu B., Woo H. Y., Kim B. J., Wang S.-J., Chan P. K. L., Guo X., Feng K.. Backbone Tailoring Enables High-Performance and Stable n-Type Organic Mixed Ionic-Electronic Conductors for Synaptic Simulation and Biosensor. Adv. Mater. 2026;38:e12070. doi: 10.1002/adma.202512070. [DOI] [PubMed] [Google Scholar]
  23. Ricks A. B., Solomon G. C., Colvin M. T., Scott A. M., Chen K., Ratner M. A., Wasielewski M. R.. Controlling Electron Transfer in Donor–Bridge–Acceptor Molecules Using Cross-Conjugated Bridges. J. Am. Chem. Soc. 2010;132(43):15427–15434. doi: 10.1021/ja107420a. [DOI] [PubMed] [Google Scholar]
  24. Guédon C. M., Valkenier H., Markussen T., Thygesen K. S., Hummelen J. C., van der Molen S. J.. Observation of quantum interference in molecular charge transport. Nat. Nanotechnol. 2012;7(5):305–309. doi: 10.1038/nnano.2012.37. [DOI] [PubMed] [Google Scholar]
  25. Zhao N., Jeon S. J., Li Y.. Cross-Conjugated Polymer Semiconductors. Macromol. Rapid Commun. 2025;46(18):e00281. doi: 10.1002/marc.202500281. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Zhao N., Jeon S. J., Yuan Y., Venkateswarlu S., Stella A., Papazotos J., Li Y.. Full Conjugation in a Polymer with Non-conjugated Piperazine-2,5-dione Units via Energy-minimized Lactam-to-Lactim Tautomerization Enables Water-gated Transistor Fluoride Sensors. Angew. Chem. Int. Ed. 2025;64(7):e202419314. doi: 10.1002/anie.202419314. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Feast W. J., Tsibouklis J., Pouwer K. L., Groenendaal L., Meijer E. W.. Synthesis, processing and material properties of conjugated polymers. Polymer. 1996;37(22):5017–5047. doi: 10.1016/0032-3861(96)00439-9. [DOI] [Google Scholar]
  28. Shi K., Zhang W., Wei C., Lin Z., Liu X., Yu G.. Dithienylmethanone-Based Cross-Conjugated Polymer Semiconductors: Synthesis, Characterization, and Application in Field-Effect Transistors. J. Polym. Sci., Part A: Polym. Chem. 2018;56(9):1012–1019. doi: 10.1002/pola.28976. [DOI] [Google Scholar]
  29. Voortman T. P., Bartesaghi D., Koster L. J. A., Chiechi R. C.. Cross-Conjugated n-Dopable Aromatic Polyketone. Macromolecules. 2015;48(19):7007–7014. doi: 10.1021/acs.macromol.5b01387. [DOI] [Google Scholar]
  30. Wang S., Ye F., Wang J., Ding R., Peng M., Li J.-T., Luan Y., Liao J., Guo Z.-H.. Unusual Cross-Conjugation in Cyclic Dipeptide-Based Building Blocks for Donor–Acceptor Semiconducting Conjugated Polymers. Angew. Chem. Int. Ed. 2025;137(2):e202413782. doi: 10.1002/ange.202413782. [DOI] [PubMed] [Google Scholar]
  31. Bischak C. G., Flagg L. Q., Yan K., Rehman T., Davies D. W., Quezada R. J., Onorato J. W., Luscombe C. K., Diao Y., Li C.-Z., Ginger D. S.. A Reversible Structural Phase Transition by Electrochemically-Driven Ion Injection into a Conjugated Polymer. J. Am. Chem. Soc. 2020;142(16):7434–7442. doi: 10.1021/jacs.9b12769. [DOI] [PubMed] [Google Scholar]
  32. Giovannitti A., Maria I. P., Hanifi D., Donahue M. J., Bryant D., Barth K. J., Makdah B. E., Savva A., Moia D., Zetek M., Barnes P. R. F., Reid O. G., Inal S., Rumbles G., Malliaras G. G., Nelson J., Rivnay J., McCulloch I.. The Role of the Side Chain on the Performance of N-type Conjugated Polymers in Aqueous Electrolytes. Chem. Mater. 2018;30(9):2945–2953. doi: 10.1021/acs.chemmater.8b00321. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Moser M., Savagian L. R., Savva A., Matta M., Ponder J. F. Jr., Hidalgo T. C., Ohayon D., Hallani R., Reisjalali M., Troisi A., Wadsworth A., Reynolds J. R., Inal S., McCulloch I.. Ethylene Glycol-Based Side Chain Length Engineering in Polythiophenes and its Impact on Organic Electrochemical Transistor Performance. Chem. Mater. 2020;32(15):6618–6628. doi: 10.1021/acs.chemmater.0c02041. [DOI] [Google Scholar]
  34. Kim H. S., Huseynova G., Noh Y.-Y., Hwang D.-H.. Modulation of Majority Charge Carrier from Hole to Electron by Incorporation of Cyano Groups in Diketopyrrolopyrrole-Based Polymers. Macromolecules. 2017;50(19):7550–7558. doi: 10.1021/acs.macromol.7b01524. [DOI] [Google Scholar]
  35. Wang P., Xu C., Zhang X., Shi Y., Wang C., Han Y., Deng Y., Geng Y.. Thienoisoindigo-Based Conjugated Polymers Synthesized by Direct Arylation Polycondensation. Macromol. Rapid Commun. 2024;45(1):2300245. doi: 10.1002/marc.202300245. [DOI] [PubMed] [Google Scholar]
  36. Ma S., Wang J., Wu W., Wu Z., Zhang H., Chen R., Liu B., Feng K., Woo H. Y., Guo X.. Sequential Cyanation of Polythiophenes: Tuning Charge Carrier Polarity in Organic Electrochemical Transistors. Adv. Electron. Mater. 2023;9(11):2300207. doi: 10.1002/aelm.202300207. [DOI] [Google Scholar]
  37. Ding R., Zhang X., Yan R., Peng M., Su S., Jeong S. Y., Woo H. Y., Guo X., Feng K., Guo Z.-H.. Ultra-Low Threshold Voltage in N-Type Organic Electrochemical Transistors Enabled by Organic Mixed Ionic-Electronic Conductors with Dual Electron-Withdrawing Substitutions. Adv. Funct. Mater. 2025;35(2):2412181. doi: 10.1002/adfm.202412181. [DOI] [Google Scholar]
  38. Cho Y., Gao L., Yao Y., Kim J., Zhang D., Forti G., Duplessis I., Wang Y., Pankow R. M., Ji X., Rivnay J., Marks T. J., Facchetti A.. Small-Molecule Mixed Ionic-Electronic Conductors for Efficient N-Type Electrochemical Transistors: Structure-Function Correlations. Angew. Chem. Int. Ed. 2025;64(2):e202414180. doi: 10.1002/anie.202414180. [DOI] [PubMed] [Google Scholar]
  39. Lan L., Wang Y., Zhu X., McCulloch I., Yue W.. Ultrathin-Film Small Molecule Mixed Conductors Exhibiting Ion-Tunable Ambipolarity for High-Performance Organic Electrochemical Transistors and Multivalued Logic Inverters. Adv. Mater. 2025;37(35):2501041. doi: 10.1002/adma.202501041. [DOI] [PubMed] [Google Scholar]
  40. Che Q., Zhang W., Wei X., Zhou Y., Luo H., Wei J., Wang L., Yu G.. High-Mobility Ambipolar Benzodifurandione-Based Copolymers with Regular Donor–Acceptor Dyads Synthesized via Aldol Polycondensation. CCS Chem. 2023;5(11):2603–2616. doi: 10.31635/ccschem.023.202202458. [DOI] [Google Scholar]
  41. Zozoulenko I., Singh A., Singh S. K., Gueskine V., Crispin X., Berggren M.. Polarons, Bipolarons, And Absorption Spectroscopy of PEDOT. ACS Appl. Polym. Mater. 2019;1(1):83–94. doi: 10.1021/acsapm.8b00061. [DOI] [Google Scholar]
  42. Luo X., Shen H., Perera K., Tran D. T., Boudouris B. W., Mei J.. Designing Donor–Acceptor Copolymers for Stable and High-Performance Organic Electrochemical Transistors. ACS Macro Lett. 2021;10(8):1061–1067. doi: 10.1021/acsmacrolett.1c00328. [DOI] [PubMed] [Google Scholar]
  43. Bernards D. A., Malliaras G. G.. Steady-State and Transient Behavior of Organic Electrochemical Transistors. Adv. Funct. Mater. 2007;17(17):3538–3544. doi: 10.1002/adfm.200601239. [DOI] [Google Scholar]
  44. Sun H., Vagin M., Wang S., Crispin X., Forchheimer R., Berggren M., Fabiano S.. Complementary Logic Circuits Based on High-Performance n-Type Organic Electrochemical Transistors. Adv. Mater. 2018;30(9):1704916. doi: 10.1002/adma.201704916. [DOI] [PubMed] [Google Scholar]
  45. Nielsen C. B., Giovannitti A., Sbircea D.-T., Bandiello E., Niazi M. R., Hanifi D. A., Sessolo M., Amassian A., Malliaras G. G., Rivnay J., McCulloch I.. Molecular Design of Semiconducting Polymers for High-Performance Organic Electrochemical Transistors. J. Am. Chem. Soc. 2016;138(32):10252–10259. doi: 10.1021/jacs.6b05280. [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. Rivnay J., Mannsfeld S. C. B., Miller C. E., Salleo A., Toney M. F.. Quantitative Determination of Organic Semiconductor Microstructure from the Molecular to Device Scale. Chem. Rev. 2012;112(10):5488–5519. doi: 10.1021/cr3001109. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ps6c00036_si_001.pdf (1.7MB, pdf)

Articles from Polymer Science & Technology are provided here courtesy of American Chemical Society

RESOURCES