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

Abstract 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.