Fig. 4: Electrochemical and optical performance of “electrode-free” electrochromic device (EECD).

a UV-Vis transmittance spectra of EECD at the colored and bleached states across the visible spectrum of 400–800 nm. b A plot of transmittance over time with applied colored and bleached voltages of 1.6 V and −0.2 V, respectively. c Transmittance-time curves of EECD and MnO₂ and Cu single electrodes at 460 nm. d Thermal management performance measurement apparatus for EECD under xenon lamp illumination to simulate sunlight. The coloring device with deposited MnO₂ (brown) and Cu (blue). e Real-time thermal images of EECD during illumination of xenon lamp. f Optical transmittance of the device in its transparent state. g Optical transmittance variation of EECD being colored at 1.6 V for 60 s, followed by a 7200 s power-off period, and then bleached at −0.2 V, with all measurements taken at a wavelength of 460 nm. h Optical transmittance over time curve of EECD after 10,000 cycles, measured at the wavelength of 460 nm. i Optical transmittance over time curves of EECD after being aged at 50 °C for 1 h, 25 °C for 1 h, and 0 °C for 1 h, respectively. All sample measured at the wavelength of 460 nm.