Pyrazine-EDOT D-A-D type Hybrid Polymer for Patterned Flexible Electrochromic Devices

Strong Proquinoidal Acceptor Enables High-Performance Ambipolar Organic Electrochemical Transistors

Ambipolar organic electrochemical transistors (OECTs) can simplify manufacturing processes and reduce device footprints, yet their performance still lags behind their p-type and n-type counterparts due to limited molecular design strategies. Here, incorporating strong proquinoidal building blocks effectively addresses this challenge is demonstrated. Using a computational acceptor screening approach, three TBDOPV-based polymers are designed and synthesized: P(bgTBDOPV-T), P(bgTBDOPV-EDOT), and P(bgTBDOPV-MeOT2), all exhibiting ambipolar behavior across various donor moieties. Remarkably, P(bgTBDOPV-EDOT) achieves record-high figure-of-merit (µC*) values, reaching 268 F cm-1 V-1 s-1 for p-type and 107 F cm-1 V-1 s-1 for n-type operations. Additionally, P(bgTBDOPV-EDOT) exhibits low operation voltages (VTh,p = -0.55 V and VTh,n = 0.32 V), with fast response times (τon/τoff = 0.48/0.36 ms for p-type and 0.41/0.41 ms for n-type) and enhanced operational stability. Inverter devices based on P(bgTBDOPV-EDOT) show high voltage gains of 173 V/V. Theoretical calculations and data analysis confirm that strong proquinoidal acceptors significantly enhance the delocalization of both positive and negative polarons, offering an effective pathway for higher-performance ambipolar OECT materials.

Carbazole-Based Dual-Band Electrochromic Polymers: The Effect of Linkage Sites on Electrochromic Performance

Dual-band electrochromic (EC) materials are expected to be utilized as building materials for energy saving, but their cycle stability is still an obstacle. Here, two D-A conjugated polymers, PDPPCz36 and PDPPCz27, based on diketopyrrolopyrrole and carbazole linked with different sites, are synthesized. Both of them exhibit dual-band EC behaviors with a dark blue color in the neutral state and high absorption in the near-infrared (NIR) region when oxidized. However, PDPPCz36 exhibits better cycle stability and a shorter response time than PDPPCz27. In the visible (VIS) region, the PDPPCz36 film exhibits an initial light modulation range (ΔT) of 43.0% and that of the PDPPCz27 film is 41.3%. After 100 cycles of redox, the ΔT of the PDPPCz36 film declines by 32%, while that of PDPPCz27 attenuates by more than 50%. A similar tendency is evident in the NIR region. Moreover, PDPPCz36 shows subsecond colored switch times both in the VIS (0.4 s) and NIR (0.7 s) regions, while those of PDPPCz27 are 2.1 and 1.6 s, respectively. Further research suggests that 3,6-linked carbazoles in PDPPCz36 simultaneously inhibit the side reaction and film aggregation, which leads to better redox stability and shorter response time in both EC tests and devices.

Application of quasi solid electrolytes in organic based electrochromic devices: A mini review

The interest in all solid organic based electrochromic devices (ECDs) is on the increase. This is because these devices offer the applicability of electrochromic materials in products such as smart sensors, smart windows, flexible wearables and energy storage devices. The use of quasi-solid electrolytes for the construction of these ECDs is attractive because of their ease of preparation, availability, low cost, improve electrochromic performance, good ionic conductivity and prevention of leakages in ECDs. Hence, in this review, a detailed discussion is presented on the progress in the development of semi-solid electrolytes for ECDs fabrication. The preparation of the most common electrolytes that have been applied for organic based ECDs are summarized. Particular attention is given to efforts and strategies that have been adopted to improve the efficiency of quasi-solid electrolytes. Importantly, knowledge gaps that warrant further research are clearly identified and recommendations for future works are suggested. This review will be very beneficial for both established and new researchers in the field of electrochromic devices and material science.

Flexible Supercapacitors Based on Stretchable Conducting Polymer Electrodes

Supercapacitors are widely used in various fields due to their high power density, fast charging and discharging speeds, and long service life. However, with the increasing demand for flexible electronics, integrated supercapacitors in devices are also facing more challenges, such as extensibility, bending stability, and operability. Despite many reports on stretchable supercapacitors, challenges still exist in their preparation process, which involves multiple steps. Therefore, we prepared stretchable conducting polymer electrodes by depositing thiophene and 3-methylthiophene on patterned 304 stainless steel (SS 304) through electropolymerization. The cycling stability of the prepared stretchable electrodes could be further improved by protecting them with poly(vinyl alcohol)/sulfuric acid (PVA/H₂SO₄) gel electrolyte. Specifically, the mechanical stability of the polythiophene (PTh) electrode was improved by 2.5%, and the stability of the poly(3-methylthiophene (P3MeT) electrode was improved by 7.0%. As a result, the assembled flexible supercapacitors maintained 93% of their stability even after 10,000 cycles of strain at 100%, which indicates potential applications in flexible electronics.

Isoindigo-Thiophene D-A-D-Type Conjugated Polymers: Electrosynthesis and Electrochromic Performances

Four novel isoindigo-thiophene D-A-D-type precursors are synthesized by Stille coupling and electrosynthesized to yield corresponding hybrid polymers with favorable electrochemical and electrochromic performances. Intrinsic structure-property relationships of precursors and corresponding polymers, including surface morphology, band gaps, electrochemical properties, and electrochromic behaviors, are systematically investigated. The resultant isoindigo-thiophene D-A-D-type polymer combines the merits of isoindigo and polythiophene, including the excellent stability of isoindigo-based polymers and the extraordinary electrochromic stability of polythiophene. The low onset oxidation potential of precursors ranges from 1.10 to 1.15 V vs. Ag/AgCl, contributing to the electrodeposition of high-quality polymer films. Further kinetic studies illustrate that isoindigo-thiophene D-A-D-type polymers possess favorable electrochromic performances, including high optical contrast (53%, 1000 nm), fast switching time (0.8 s), and high coloration efficiency (124 cm² C^-1). These features of isoindigo-thiophene D-A-D-type conjugated polymers could provide a possibility for rational design and application as electrochromic materials.

Cobweb-Inspired Quintuple Network Structures toward High-Performance Wearable Electrochromic Devices with Excellent Bending Resistance

Flexible electrochromic devices (FECDs) have been regarded as an ideal stratagem for wearable displays. However, it remains a great challenge to achieve long-term stability for high-performance FECDs due to their severe electrolyte deformation/leakage under repeated bending. Herein, inspired by the rough and fluffy microstructure of cobwebs, we prepared a porous polylactic acid (PLA) network through electrospinning and nonsolvent-induced phase separation. This loosely interlaced PLA network can be well infiltrated by electrolytes and exhibits extraordinarily high transparency; in addition, its surface contains numerous tiny holes to effectively load electrolytes to mitigate deformation. Furthermore, we also introduced silver nanowires (AgNWs) as the supporting network to load and connect electrochromic materials. After assembling them with graphene (GR) electrodes, a wearable FECD with a quintuple network structure (two GR networks, two AgNW networks, and one PLA network) was successfully prepared. The resulting FECD can realize high optical modulation (more than 70%), excellent cyclic stability (retain 95% after 1000 cycles), and innovative bending resistance (retain 84.8% after 6000 bending cycles). This work not only solves the long-lasting challenge of developing FECD with high optical modulation and bending resistances but also provides an energetic paradigm for diverse soft electronics used in harsh environments.