A Dual‐Mode Electrochromic Platform Integrating Zinc Anode‐Based and Rocking‐Chair Electrochromic Devices

Abstract

The complementary electrochromic device, where the optical transmittance changes upon the flow of cations back and forth between anodic and cathodic electrodes, operates in a rocking-chair fashion if it can inherently self-discharge. Herein, the first demonstration of a dual-mode electrochromic platform having self-coloring and self-bleaching characteristics is reported, which is realized by sandwiching zinc metal within a newly-designed Prussian blue (PB)-WO 3 rocking-chair type electrochromic device. It is demonstrated that the redox potential differences between the zinc metal and the WO 3 /PB electrodes endow the self-color-switching of these electrodes. By employing a hybrid electrolyte of Zn 2+ /K + , it is further shown that the colored PB-WO 3 rocking-chair device is capable of spontaneously bleaching when the anodic and cathodic electrodes are coupled. This dual-mode light-control strategy enables the electrochromic devices to exhibit four distinct optical states with the highest optical contrast of 72.6% and fast switching times (<5 s for the bleaching/coloration processes). Furthermore, the built-in voltage of the dualmode electrochromic devices not only promotes energy efficiency, but also augments the bistability of the devices. It is envisioned that the broad implication of the present platform is in the development of self-powered smart windows, colorful displays, optoelectronic switches, and optical sensors.

Homogeneous and Nanogranular Prussian Blue to Enable Long-Term-Stable Electrochromic Devices

“…It can be calculated by the following standard equation η = normalΔ O D Q normals = log nobreak0em0.25em⁡ T b l e a c h e d T c o l o r e d Q normals where T bleached and T colored , respectively, represent the transmittance of the PB thin film in bleached and colored states. As shown in Figure c, the coloration efficiency of the PB thin film is estimated to be 417.79 cm 2 C –1 , much larger than that reported in the previous work . The high coloration efficiency means a broad optical modulation within a small amount of charge variation .…”

Amorphous and Crystalline Ti-Doped WO3·2H2O for Dual-Band Electrochromic Smart Windows

“…Building energy consumption accounts for more than 40% of global energy consumption, half of which is used for lighting, heating, and cooling. , VIS and NIR light carry most light and heat of solar energy, and can enter the buildings through windows, affecting indoor light and temperature. − The electrochromic smart windows (ESW) can dynamically modulate the optical transmittance to achieve energy saving. , However, the NIR region carries about 43% of solar heat and contributes nothing to illumination; the general ESW can only modulate transmittance in wide wavelengths; therefore the energy saving is not obvious . DESW can selectively modulate the VIS and NIR light, which can effectively reduce building energy consumption. − …”

Transparent metal oxide interlayer enabling durable and fast-switching zinc anode-based electrochromic devices

“…Transition metal compounds are extensively studied as ECMs due to fast switching and excellent cycling stability, such as WO 3 , 24 TiO 2 , 25 V 2 O 5 , 26 MoO 3 , 27 NiO, 28 and Prussian blue (PB). 29 Interestingly, PB has a high voltage plateau for excellent energy density and is widely employed as cathodes of secondary batteries. 30,31 PB has a cubic crystal structure with the formula of AFe( iii )[Fe(CN) 6 ], where A is generally an alkali metal or ammonia.…”