Super‐Wide Color Tunability from a Single Electrochromic Device through In Situ Reconstruction of Optical Cavity

Electrochromic (EC) displays, as non-emissive (passive) displays with low energy consumption, have garnered significant attention from both industry and academia in recent years. Nevertheless, traditional EC technology faces challenges in achieving full-color displays within a single device due to its limited color gamut, even though full-color capability is highly desirable for eliminating the need for complex RGB subpixel mosaics. Herein, a new strategy is proposed utilizing in situ, electrically driven reconstruction of optical cavities on an electrochromic electrode surface to fabricate EC devices with super-wide color tunability. The device fabricated by this approach can create a wide variety of colors from yellow, orange, red, violet, blue, and cyan to green in a single EC device that almost spans the entire visible region (Δhue approaches 360°). Apart from the super-wide color tunability, the devices also have small working voltage window (0.2-1.8 V), outstanding bistability (>8 h), extremely low power consumption (≈2.3 mW cm^-2) and good cycling ability (≈4.3% decay rate after 1,000 cycles). Moreover, the super-wide color tunability of these EC devices has been demonstrated in diverse applications, including shifting rainbow flower images, color palettes, and information displays.