Carbazole based electrochromic polymers with benzoazole units: Effect of heteroatom variation on electrochromic performance

Abstract

Abstract.A series of carbazole-based polymers were synthesized via Suzuki polymerization between N-(2-ethylhexyl)carbazole-3,6-bis(ethyleneboronate) (Cbz) and dibromobenzazole unit. Three different polymers, PCBN, PCBS and PCBSe were obtained from 4,7-dibromo-2-hexyl-2H-benzotriazole (BN), 4,7-dibromo-2,1,3-benzothiadiazole-(BS) and 4,7-dibromo-2,1,3-benzoselenadiazole (BSe), respectively. It is observed that, the variation of heteroatoms (N,S and Se) on the benzazole unit have most important effect on electro-optic properties of the PCBX polymers. Neutral state color of the polymer films and their electrochromic performances are also influenced. Among the synthesized polymers, the PCBS bearing 2,1,3-benzothiadiazole as acceptor units has a broad absorption and 50% of ΔT in the near-IR regime at the oxidized state. This property of PCBS is a great advantage for near-IR electrochromic applications.

Photopolymerization of electroactive film applied to full polymer electrochromic device

“…Following reactions 3 and 4, hydrogen abstraction reactions formed both radical cations (PhI +• ) and protonic acids (H + ) which are greatly active towards monomers and can directly initiate polymerization. To construct an electrochromic device, it is necessary to compensate the coulombic change used for the redox (i.e., coloring/bleaching) process of a complementary modified electrode [18]. The optical contrast of the device is promoted if this complementary electrode system also has complementary electrochromic color changes.…”

Orange to green switching anthraquinone‐based electrochromic material

“…1,4-Diamino anthraquinone (1) was diazotized with tert-butyl nitrite followed by quenching with anhydrous copper(II) bromide to form 1,4-dibromoanthraquinone (2). 14 The Stille coupling reaction between the purified 1,4-dibromo anthraquinone and 4-octyl-2-trimethyl stannyl thiophene gave compound 3 in 62.5% yield, subsequently brominated with NBS resulted in 1,4-bis(5-bromo-4-octylthiophen-2-yl) anthracene-9,10-dione (4). The proton and carbon 13 spectra of the monomer (compound 4) are given as Supporting Information.…”

“…The past few decades have witnessed an upswing in the interest of using semiconducting conjugated polymers for multitude of applications such as photovoltaics, transistors, and light‐emitting diodes . The development and characterization of electrochromic materials is among the various research fields that have been intensively investigated for applications such as smart windows, switchable mirrors, and camouflage for both organic and inorganic materials . Organic semiconducting materials have found great popularity in electrochromic devices and are widely researched due to the potential of easy processability, color tunability via chemical structure modifications, good stability, and the low potential requirement for inducing color changes …”

“…3 The development and characterization of electrochromic materials is among the various research fields that have been intensively investigated for applications such as smart windows, switchable mirrors, and camouflage for both organic and inorganic materials. 4 Organic semiconducting materials have found great popularity in electrochromic devices and are widely researched due to the potential of easy processability, color tunability via chemical structure modifications, good stability, and the low potential requirement for inducing color changes. 5 In the past, a wide range of electrochromic materials have been studied for electrochromic applications.…”

“…In the past, a wide range of electrochromic materials have been studied for electrochromic applications. Some of the classes of polymers investigated are based on thiophene‐quinoxaline (TQ), thiophene‐benzotriazole or 5,6‐dialkoxy‐benzothiadiazole,5b carbazole‐benzothiadiazole, and propylenedioxythiophene (proDOT) . Among these, TQ1‐based electrochromic materials, reported by Hellström et.al , showed a color change from blue in neutral condition to colorless when oxidized with an applied external potential of 1 V, resulting in a 50% optical transmittance change at a wavelength of 623 nm.…”