This report highlights the synthesis of only the second green polymer in the literature, which possesses superior properties over the first: a highly transmissive light blue color in the oxidized state with high optical contrast and excellent switching properties.

Polymers that have one of the three complementary colors (red, green, and blue, RGB) in the reduced state and high transmissivity in the oxidized state are key materials towards use in electrochromic devices and displays. Although many neutral-state red and blue polymers have been reported up to date, neutral-state green polymeric materials appear to be limited only to the ground-breaking work of Sonmez et al. [1] and a benzothiadiazole-based polymer from our group.[2] Besides these materials, green polymers with highly transmissive oxidized states, excellent optical contrasts, fast switching times, and advanced long-term switching stabilities are essentially missing in the literature. In this report, the synthesis of two novel donor-acceptor-type polymers with satured green colors in the reduced state, namely poly[2,3-bis(4-tert-(PTBPEQ) and poly [2,3-diphenyl-5,8-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)quinoxaline] (PDPEQ), is addressed. PTBPEQ is shown to be an outstanding green electrochromic material with the highest optical constrast in the visible region reported to date. PTBPEQ is highly transmissive in the oxidized state, and the electroactivity of the polymer remains intact even after cycling 5000 times between its fully reduced and oxidized states. Very fast switching times and ease of electrochemical synthesis make this polymer a paramount choice as the green component for the completion of RGB color space. A great deal of attention has been focused on conjugated polymers since they are potentially useful materials for a broad range of applications like photovoltaic devices, [3] lightemitting diodes (LEDs), [4] field effect transistors, [5] sensors, [6] and electrochromic devices. [7] A reversible optical change observed in a material because of an applied external voltage is defined as electrochromism. In particular, optically responsive conductive polymer systems that reveal electrochromism are particularly required for their potential use in data storage and display technologies. Even though many inorganic materials, especially tungsten oxides, have been utilized over the past three decades, [8] the use of conjugated polymers as active layers in electrochromic devices has received enormous attention because of their high optical contrasts, [9] fast switching times, [10,11] processability, [12] and fine-tuning of the bandgap by structure modification.[13] On the other hand, for potential application of electrochromic materials in display technologies, one should have to create the entire color spectrum and this can be only achieved by having materials with additive or subtractive primary colors in their neutral states. Unfortunately, most of the polymers studied so far mainly absorb/reflect blue and red colors. Having one dominant wavelength is the main reason for this. To obtain a green color there should be at least two simultaneous absorption bands in the red and blue regions of the visible spectrum, and these bands should also be controlled with the same applied potential. All this complex...

A new donor-acceptor type polymer poly (4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-dodecyl-2H-benzo [1,2,3] triazole) (PBEBT) was synthesized and its electrochromic properties were investigated. Spectroelectrochemistry studies for PBEBT showed an absorption maximum at 618 nm which is nearly identical to that of poly(ethylenedioxythiophene) (PEDOT) where polymer has a saturated blue color in its neutral state. However, PBEBT film revealed better properties than that of PEDOT in terms of optical contrast, switching time and coloration efficiency. Additionally, electrochemical and spectral results conclude that PBEBT is a both p-and n-type dopable polymer. PBEBT proved to be a superior option for electrochromic display device applications.

Two new highly stable electrochromic polymers, poly(5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2,3-di(thiophen-2-yl)quinoxaline) (PDETQ) and poly(5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)quinoxaline) (PDEQ) were synthesized, and their potential use as neutral state green polymeric materials was investigated. Spectroelectrochemistry showed that both polymers reveal two distinct absorption bands as expected for this type of donor–acceptor polymer, at 410 and 660 nm for PDEQ and 405 and 780 nm for PDETQ. The colorimetry analysis revealed that while PDEQ has a green-blue color, PDETQ showed a saturated green color in the neutral state which is a unique property of conjugated polymers for the completion of the RGB color system. Both polymers have excellent switching properties with satisfactory optical contrasts and very fast switching times. In addition, via both electrochemical and spectral analyses PDETQ was proven to be an n-type dopable polymer. Outstanding optical contrasts in the NIR region, perfect stability, and fast switching times make these polymers excellent candidates for many applications like smart windows and data storage technologies. It should be noted that PDETQ is one of the few examples of neutral state green polymeric materials in literature with a relatively transmissive oxidized state, high stability, and superior switching properties. Hence, PDETQ can be a paramount choice as a green polymeric material for display applications.

Realization of commercial RGB‐based polymer electrochromic‐device applications can only be achieved by processable materials that possess three complementary colors in the reduced state and are transparent in the oxidized state. This report highlights the synthesis of the first processable green polymer with a transmissive oxidized state. The polymer revealed superior optical contrast in the visible region with fast switching times and robust stability. Hence, this material is the outstanding candidate for completion of RGB color space through commercial polymeric electrochromics.