Photo-induced self-reduction enabling ultralow threshold voltage energy-conservation electrochromism

[Display omitted] •The illumination of Viologen/TiO2 gels lead to an ultralow voltage electrochromic effect.•Threshold voltage can be reduced to ∼0.1 V, the lowest value reported.•A lowest working energy consumption of 0.18 mJ cm−2 is achieved.•RGB array displays and large-area flexible devices are demonstrated. Electrochromic (EC) devices are highly desired for fields like smart windows, sensing, and display because of their great light modulation ability. However, the high driving voltage of the EC device usually leads to the decomposition of internal electrolyte, degradation of cyclability and higher energy consumption. In this work, based on the finding of the photo-induced self-reduction and coloration of light illuminated viologen/TiO2 gels (VTGs), we develop VTG-based devices which show remarkable EC performance under an ultralow voltage (∼0.1 V). The working energy consumption of a VTG device is at least one order of magnitude lower than those of reported EC devices and other display technologies, giving rise to the larger area/scale optical modulation. Furthermore, through the construction of RGB array displays, large-area EC devices, and flexible EC devices, the universal applicability and multifield potential applications of VTGs were demonstrated.