Reflective and Complementary Transmissive All‐Printed Electrochromic Displays Based on Prussian Blue

Abstract

By combining the electrochromic (EC) properties of Prussian blue (PB) and poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), complementary EC displays manufactured by slot‐die coating and screen printing on flexible plastic substrates are reported. Various display designs have been realized, resulting in displays operating in either transmissive or reflective mode. For the transmission mode displays, the color contrast is enhanced by the complementary switching of the two EC electrodes PB and PEDOT:PSS. Both electrodes are either exhibiting a concurrent colorless or blue appearance. For the displays operating in reflection mode, a white opaque electrolyte is used in conjunction with the EC properties of PB, resulting in a display device switching between a fully white state and a blue‐colored state. The developments of the different device architectures, that either operate in reflection or transmission mode, demonstrate a scalable manufacturing approach of all‐printed EC displays that may be used in a large variety of Internet of Things applications.

Electrochromic Strategies for Modulation between Primary Colors: Covering the Visible Spectrum

“…The conventional ECDs, as discussed above, work on the principle of obtaining a visible output, measured in terms of either transmittance or reflectance, and are passive in nature in the sense that they do not emit any color on their own. Electrofluorochromism (EFC), on the other hand, deals with devices employed with fluorescent materials which in turn provide emissive output while working on a principle similar to the ECDs. − This implies that EFC-active materials are capable of responding to external bias stimuli in a similar way, as that by ECMs, however producing brilliant output contrasts which are multitudes higher, and they find better applications in optoelectronics.…”

“…The conventional ECDs, as discussed above, work on the principle of obtaining a visible output, measured in terms of either transmittance or reflectance, 30 and are passive in nature in the sense that they do not emit any color on their own. Electrofluorochromism (EFC), on the other hand, deals with devices employed with fluorescent materials which in turn provide emissive output while working on a principle similar to the ECDs.…”

“…Using this methodology, either of the two types of ECDs can be fabricated, i.e., transmissive or reflective depending on the type of ECM. In the case of a reflective type of ECD, the second substrate is usually a shiny material instead of transparent glass. , Besides, fabrication of ECDs delivering RGB outputs follows the same recipe wherein the chosen chromophores are those materials which produce an RGB when applied with bias.…”

“…29 These materials can be used to fabricate ECDs for operation in two modes, either "transmissive" or "reflective" for which the design is chosen as per the specific application. 30 These devices can also be categorized as organic or inorganic, depending on the corresponding class of electrochromic materials (ECMs) used. They possess certain advantages or disadvantages over the other, thus indulging in domain specific usage.…”

“…The process is governed by redox reactions involving bidirectional electron flow leading to intrinsic changes in bandgap of the material . These materials can be used to fabricate ECDs for operation in two modes, either “transmissive” or “reflective” for which the design is chosen as per the specific application . These devices can also be categorized as organic or inorganic, depending on the corresponding class of electrochromic materials (ECMs) used.…”