Enhanced black state induced by spatial silver nanoparticles in an electrochromic device

Abstract

The use of three-dimensional (3D) hierarchical indium tin oxide (ITO) branches of electrochromic devices (ECDs) is an effective approach for increasing the optical properties via localized surface plasmon resonance compared with two-dimensional nanostructured electrodes. ECDs with 3D branches were designed to operate in transparent, mirror and black states. Finite-difference time-domain simulation was used to find the electrical field distributions in three types of ECD: glass/ITO with Ag film, glass/ITO branches and glass/ITO branches with Ag nanoparticles. The ECDs had an optical transmittance of 73.76% in the transparent state, a reflectance of 79.77% in the mirror state and a reflectance of 8.78% in the black state. We achieved an ECD with high stability that can show ∼ 10 000 switching cycles among the three states. NPG Asia Materials (2017) 9, e362; doi:10.1038/am.2017.25; published online 17 March 2017 INTRODUCTION Electrochromic devices (ECDs) can exhibit reversible color changes induced by electric energy and the resulting electrochemical redox reactions of materials. 1,2 The changes in optical states are consequences of a change in the electronic state as a result of electron transfer between the electrochromic (EC) material and an electrode. ECDs offer many advantages over conventional displays, including a low operating voltage (V OP ), memory effects, color variations and visibility in sunlight. [3][4][5][6][7] Therefore, ECDs are expected to achieve applications in information displays or in light-modulating devices such as smart windows, switchable mirrors, electronic papers and chemical sensors. [8][9][10][11][12] Conventional ECDs are composed of a non-metal (NM) EC material (for example, poly(ethylene oxide), poly(methyl methacrylate), polyvinylidene difluoride, WO 3 , MoO 3 , Ir(OH) 3 , NiO). [13][14][15][16][17] In particular, WO 3 , which is the most widely known EC material, has attracted considerable attention because of its broad applications such as in ECDs, photocatalysis and sensing devices. 3 However, the use of NM-ECD encounters two drawbacks. (1) It has low optical transmittance when in the transparent state because of the inherent color and high extinction coefficient (k) of the NM materials compared with the metal ions in the electrolyte of the transparent state. [13][14][15][16][17][18] (2) The NM-ECD cannot exhibit a mirror state. Because free electrons are rarely generated in NM materials, an electric field easily penetrates the NM materials. Therefore, most of the incident energy is absorbed or transmitted. As a result, NM-ECDs are not suitable for use in displays and windows.Silver (Ag) has been used as an EC material because of its superior optical properties. Because Ag readily assembles into nanoparticles

Reliable Information Encryption and Digital Display Applications Based on Multistate Smart Windows

“…These Ag NPs can absorb all incident lights, which is induced by the LSPR effects. As a result, all the reflective lights were suppressed and the REMD changed from the mirror state to a black state . The LSPR can also be a method to bring richer chromatic states by effectively controlling the nucleation and growth processes .…”

“…Especially, the one based on several metals (Ag, Cu, Al, or Ni, etc.) modulate their optical properties by transforming their states between metal and metal ion …”

“…Kobayashi and co‐workers proposed the realization of the three optical states devices and multicolor tunable devices by adopting Ag based REMD . Jeong et al reported the black state of REMD can be largely improved via introducing 3D indium tin oxide (ITO) branches . Park et al has enhanced the ability to keep mirror state (smooth ITO side) by self‐assembling thiol‐terminated silane as connecting bridge between ITO glass and Ag particles .…”

“…Besides, the applications for efficiently using them are still rather limited. Thus, it is of great importance to explore the novel applications of the multicolor devices and broaden their functionalities …”

Multifunctional electrochromic energy storage devices by chemical cross-linking: impact of a WO3·H2O nanoparticle-embedded chitosan thin film on amorphous WO3 films

“…Recently, the implementation of electrochemical energy storage in EC devices has received significant interest as a potential avenue for expanding their applications. When the device performs optical modulation, a pseudocapacitance is usually generated via a reversible redox reaction at the electrode surface that results in the storage of charge 7 . Such a device can realize multiple functions of optical modulation and energy storage/release simultaneously, and thus can automatically monitor the level of stored energy via variation of the optical properties (transmittance or color).…”