Quadruple Control Electrochromic Devices Utilizing Ce4W9O33 Electrodes for Visible and Near‐Infrared Transmission Intelligent Modulation

Abstract Electrochromic smart windows are promising for building energy savings due to their dynamic regulation of the solar spectrum. Restricted by materials or traditional complementary device configuration, precisely and independently controlling of visible (VIS) and near‐infrared (NIR) light is still on the drawing board. Herein, a novel Zn2+ electrochemically active Ce4W9O33 electrode is reported, which demonstrates three distinct states, including VIS and NIR transparent “bright and warm” state, VIS and NIR opaque “dark and cool” state, VIS transparent and NIR opaque “bright and cool” state. A dual‐operation mode electrochromic platform is also presented by integrating Ce4W9O33/NiO complementary device and Zn anode‐based electrochromic device (Ce4W9O33/Zn/NiO device). Such a platform enables an added VIS opaque and NIR transparent “dark and warm” state, thus realizing four color states through individually controlling Ce4W9O33 and NiO electrodes, respectively. These results present an effective approach for facilitating electrochromic windows more intelligent to weather/season conditions and personal preferences.

The growth mechanism of NiO is similar to that of the Ce 4 W 9 O 33 film.The difference is that a weakly alkaline environment was formed due to the addition of urea in the precursor solution.
Thus, Ni(OH) 2 nanocrystals were probably first formed and subsequently decomposed to NiO under hydrothermal temperature and pressure.Figure S11 shows that the FTO surface is uniformly covered by the NiO film, which is composed of NiO nanoflakes with a thickness of about 50-60 nm.As an active metal, Zn can be easily oxidized by releasing electrons to form Zn 2+ ions, while W 6+ can be reduced to W 5+ through accepting electrons.Therefore, the Ce 4 W 9 O 33 electrode can be self-colored by connecting the Zn and Ce 4 W 9 O 33 electrodes (Figure S13a).The device can switch to the "bight and warm" state after applying a voltage of 1.2 V between the Zn and Ce 4 W 9 O 33 electrodes (Figure S13b).Additionally, the "dark and warm" state can also return to the "bight and warm" state through the self-bleaching of NiO electrode by connecting it to Zn electrode (Figure S13c).The NiO film exhibits a poor cycle stability, where the optical modulation decreases from 66.3% to 41.6%, maintaining only 62.7% of its initial value after 500 cycles.

Figure S2 .
Figure S2.STEM-EDS elemental mapping results for the Ce 4 W 9 O 33 film.

Figure
Figure S3.a) TEM image and b) selected-area electron diffraction (SAED) patterns of the Ce 4 W 9 O 33 film.

Figure S5 .
Figure S5.GCD curves of the as-prepared Ce 4 W 9 O 33 film electrode at current densities of 0.03 and 0.05 mA•cm -2 , respectively.

Figure S6 .
Figure S6.GCD profiles and the corresponding in situ transmittance change curve at 633 nm for the Ce 4 W 9 O 33 film electrode at 0.3 mA•cm -2 .

Figure S8 .
Figure S8.Optical density variations with respect to the charge density for the Ce 4 W 9 O 33 film measured at 1200 nm.

Figure S9 .
Figure S9.Optical density variations with respect to the charge density for the Ce 4 W 9 O 33 film measured at 633 nm.

Figure S10 .
Figure S10.a) Transmittance spectra and b) absorption spectra of the hydrothermally grown NiO film in its colored and bleached states.

Figure S11 .
Figure S11.SEM images for the hydrothermally grown NiO film.

Figure S12 .
Figure S12.CV curves of the Ce 4 W 9 O 33 and NiO films, measured at a scan rate of 5 mV•s -1 .

Figure S13 .
Figure S13.Transmittance spectra of the Ce 4 W 9 O 33 /Zn/NiO device at the following states: a) self-colored by connecting the Zn and Ce 4 W 9 O 33 electrodes.b) Bleached by applying a voltage of 1.2 V between the Zn and Ce 4 W 9 O 33 electrodes in the "bright and cool" state.c) Self-bleached by connecting the Zn and NiO electrodes at the "dark and warm" state.

Figure S14 .
Figure S14.Real-time transmittance changes of the Ce 4 W 9 O 33 /Zn/NiO device at the following states: a) Self-colored by connecting the Zn and Ce 4 W 9 O 33 electrodes.b) Selfbleached by connecting the Zn and NiO electrodes at the "dark and warm" state.

Figure S15 .
Figure S15.Real-time transmittance changes during reversible switching of the NiO film measured at 550 nm.

Figure S16 .
Figure S16.Optical density variations with respect to the charge density of the NiO film recorded at 550 nm.

Figure S17 .
Figure S17.Cycle performance of the NiO film measured at 550 nm.

Figure S18 .
Figure S18.Open circuit voltage of the full charged device measured between the Zn and NiO electrodes.