Self-Driven Multicolor Electrochromic Energy Storage Windows Powered by a "Perpetual" Rechargeable Battery.

Electrochromic windows (ECWs) become an appealing concept for green buildings. However, conventional ECWs need external biases to operate causing energy consumption and are usually restricted by monotonous color. Recently, electrochromic energy storage windows (EESWs) integrating the functions of electrochromism and energy storage in one device have attracted particular attention in various fields, such as self-powered addressable displays, human-readable batteries, and most importantly energy-efficient smart windows. Herein, a color-tunable (nonemissive-red-yellow-green) self-powered EESW is initially presented utilizing Prussian blue (PB) as a controller of the fluorescent component of CdSe quantum dots. The key design feature is that without any external stimuli, the EESW can be powered by a rechargeable "perpetual" battery, which is composed of two half-cell couples of Fe/PB and Prussian white (PW)/Pt. This technique allows to achieve only by switching the connection status of the two half-cells, the fast discharging and self-charging process of the EESWs with high and sustainable charge-storage capacity. Remarkably, the fabricated self-powered EESWs exhibit quick response ("off" 7 s, "on" 50 s), large transmittance spectra contrast, and high fluorescent contrast modulation (60-86%) over a wide optical range, and great reproducibility (only 3% of the modulation ratio decreased after 30 cycles), which is comparable to ECWs powered by an electrochemical potentiostat.