A Piezoelectric-Driven Electrochromic/Electrofluorochromic Dual-Modal Display Device

Gold Nanoparticles with N-Heterocyclic Carbene/Triphenylamine Surface Ligands: Stable and Electrochromically Active Hybrid Materials for Optoelectronics

Organic-hybrid particle-based materials are increasingly important in (opto)electronics, sensing, and catalysis due to their printability and stretchability as well as their potential for unique synergistic functional effects. However, these functional properties are often limited due to poor electronic coupling between the organic shell and the nanoparticle. N-heterocyclic carbenes (NHCs) belong to the most promising anchors to achieve electronic delocalization across the interface, as they form robust and highly conductive bonds with metals and offer a plethora of functionalization possibilities. Despite the outstanding potential of the conductive NHC-metal bond, synthetic challenges have so far limited its application to the improvement of colloidal stabilities, disregarding the potential of the conductive anchor. Here, NHC anchors are used to modify redox-active gold nanoparticles (AuNPs) with conjugated triphenylamines (TPA). The resulting AuNPs exhibit excellent thermal and redox stability benefiting from the robust NHC-gold bond. As electrochromic materials, the hybrid materials show pronounced color changes from red to dark green, a highly stable cycling stability (1000 cycles), and a fast response speed (5.6 s/2.1 s). Furthermore, TPA-NHC@AuNP exhibits an ionization potential of 5.3 eV and a distinct out-of-plane conductivity, making them a promising candidate for application as hole transport layers in optoelectronic devices.

Polyvinylidene Fluoride Based Piezoelectric Composites with Strong Interfacial Adhesion via Click Chemistry for Self-Powered Flexible Sensors

Achieving relatively uniform dispersion in organic-inorganic composites with overwhelming differences in surface energy is a perennial challenge. Herein, novel eliminated polyvinylidene fluoride (EPVDF)/EPVDF functionalized barium titanate nanoparticles (EPVDF@BT) flexible piezoelectric nanogenerators (PENGs) with strong interfacial adhesion are developed via thermal stretching following sequential click chemistry. Thanks to the strong interfacial adhesion, the optimal PENGs containing ultra-high β-phase content (97.2%) exhibit not only optimized mechanical and dielectric behaviors but also excellent piezoelectric properties with high piezoelectric output (V = 10.7 V, I = 216 nA), reliable durability (8000 cycles), ultrafast response time (20 ms), and good sensitivity (2.09 nA kPa-1), far outperforming most reported PVDF-based composites. Furthermore, COMSOL finite element simulations (FEM) confirm that the elevated stress transfer efficiency induced by the strong interfacial adhesion is the main driving force for enhanced piezoelectric performances. For practical applications, self-powered PENGs can simply but stably capture mechanical energy, drive tiny electronic devices, and serve as potential multifunctional and durable sensors for detecting human physiological motions. This work opens a pioneering avenue to break the trade-offs between piezoelectric and other properties, which is of great importance for developing self-powered flexible sensors.

Research Progress in Special Engineering Plastic-Based Electrochromic Polymers

SPECPs are electrochromic polymers that contain special engineering plastic structural characteristic groups (SPECPs). Due to their high thermal stability, mechanical properties, and weather resistance, they are also known as high-performance electrochromic polymer (HPEP or HPP). Meanwhile, due to the structural characteristics of their long polymer chains, these materials have natural advantages in the application of flexible electrochromic devices. According to the structure of special engineering plastic groups, SPECPs are divided into five categories: polyamide, polyimide, polyamide imide, polyarylsulfone, and polyarylketone. This article mainly introduces the latest research on SPECPs. The structural design, electrochromic properties, and applications of these materials are also introduced in this article, and the challenges and future development trends of SPECPs are prospected.

A Large-Area Patterned Hydrogen-Bonded Organic Framework Electrochromic Film and Device

Fabrication of a patterned hydrogen-bonded organic framework (HOF) films on a large scale is an extreme challenge. In this work, a large area HOF film (30 × 30 cm2 ) is prepared via an efficient and low-cost electrostatic spray deposition (ESD) approach on the un-modified conductive substrates directly. Combining the ESD with a template method, variously patterned HOF films can be easily produced, including deer- and horse-shaped films. The obtained films exhibit excellent electrochromic performance with multicolor change from yellow to green and violet, and two-band regulation at 550 and 830 nm. Benefiting from the inherently present channels of HOF materials and the additional film porosity created by ESD, the PFC-1 film could quickly change color (within 10 s). Furthermore, the large-area patterned EC device is constructed based on the above film to prove practical potential application. The presented ESD method can be extended to other HOF materials; thus, this work paves a feasible path for constructing large-area patterned HOF films for practical optoelectronic applications.