Hydrogen‐Bonding Induced Crosslinked Polymer Network for Highly Stable Electrochromic Device and a Construction Strategy for Black‐Bilayer Electrochromic Film

Abstract

This work presents a new strategy to achieve highly stable electrochromic devices and bilayer film construction. A novel solution‐processable electrochromic polymer P1‐Boc with quinacridone as the conjugated backbone and t‐Boc as N‐substituted non‐conjugated solubilizing groups is designed. Thermal annealing of P1‐Boc film results in the cleavage of t‐Boc groups and the formation of N─H⋯O═C hydrogen‐bonding crosslinked network, which changes its intrinsic solubility characteristics into a solvent‐resistant P1 film. This film retains the electrochemical behavior and spectroelectrochemistry properties of the original P1‐Boc film. Intriguingly, the electrochromic device based on the P1 film exhibits an ultrafast switching time (0.56/0.80 s at 523 nm) and robust electrochromic stability (retaining 88.4% of the initial optical contrast after 100 000 cycles). The observed cycle lifetime is one of the highest reported for all‐organic electrochromic devices. In addition, a black‐transparent bilayer electrochromic film P1/P2 is developed in which the use of the solvent‐resistant P1 film as the bottom layer avoids interface erosion of the solution‐processable polymer in a multilayer stacking.

Mechanistic Insights into Anion-Induced Electrochromism of Ru(II)-Based Metallo-Supramolecular Polymer

“…In addition, the color of the polyRu film changes from rose red in the initial state to green in the oxidation state, and to dark red in the reduction state (close to the initial color), as shown in the inset of Figure 3 d. To address this issue of the transport of ClO 4 − anions being disadvantageous for the performance of polyRu films, some possible strategies have been proposed. Firstly, enhancing the interaction between the metal ions and ligands can help to improve the stability of the polymer chain in the electrolyte, as demonstrated in the previous report [ 30 ]. Alternatively, creating a looser structure in electrochromic materials can facilitate the transfer or migration of ion carriers across the film, thereby improving the impact of anion transport to some extent [ 31 ].…”

“Dark-to-Warm” Smart Windows Enabled by Black-to-Black Electrochromic Copolymers with Minimal Visible and Remarkable NIR Modulation

“…28 Our group also synthesized broad-absorption polymers with a substantial optical contrast (>50%) based on fused tris(thienothiophene) via DArP. 29 A bilayer polymer strategy has been employed to prepare black electrochromic materials, 30 and a dual polymer complementary method has been utilized for fabrication of black-to-transmissive electrochromic devices (ECDs). 31 Both methods have yielded black electrochromic materials or devices characterized by pure color, high optical contrast, fast switching response, and high coloration efficiency (CE).…”

Dual Polymer Complementarity Induced Truly Black Electrochromic Film and the Construction of Intelligent Eye-Protection Filters

“…An effective strategy is multilayer composite method by combining three primary colors (including additive RGB of red-, green-, and blue- and subtractive CMY of cyan-, magenta-, and yellow-)-to-transparent displays. , According to the color mixing theory, the resulting multilayer film shows full absorption in the visible region (380–780 nm) equal to black in the neutral state, and exhibits transparency in the oxidized state. , Mei et al described a solution-processable electrochromic polymer (ECP) stacking scheme in which a cross-linker is coprocessed with three primary (CMY) ECPs, imparting solvent-resistant properties to the single layer, allowing them to be sequentially deposited, resulting in a black-to-transparent film by varying the film thickness of each layer . Thus, it can be seen that the main obstacle to solution-processed organic electrochromic materials by color superposition is the high mutual solubility of conjugated organic electrochromic materials, which leads to the erosion of the interface between different materials. − In addition, they employed an ingenious strategy by pairing a green cathodic electrochromic material with magenta/red anodic electrochromic materials to obtain a black-to-transparent dual polymer complementary electrochromic device, which has the highest reported coloration efficiency . The complementary material is rare and uncommon, and this work provides inspiration and guidance for the subsequent preparation of high-performance complementary electrochromic devices.…”