Tunable Structural Colors with ‘Light‐Lossy’ MXene Paints

Thin-film interference with a Fabry-Pérot cavity is a classic approach to generating structural colors for anti-counterfeiting, sensors, and aesthetical demands. However, an absorbing layer capable of balancing the reflectance and absorption bands remains elusive, thereby limiting the chromatic and luminant tunability of structural coloration. Here wide-color-gamut films are reported with MXene as the absorbing layer in a simple trilayer configuration for vivid structural colors, outperforming conventional metal- and semiconductor-based films. It is demonstrated that the 'lossy' refractive indices of different metallic MXene compositions broaden the absorption bandwidth of multilayer films and maintain the high reflectance, enabling a substantial and complementary gamut with high tunability beyond the area of sRGB color space. Various structural color films/patterns based on MXenes showcase the compatibility for different scenarios. The results accompanied by theoretical calculations provide insights into the fundamental understanding of light-MXene interaction in coloration. The unique optical absorbance and solution processibility of the MXene family offer a versatile platform for the physical manipulation of light beyond conventional manufacturing approaches.