Diarylethenes with a Narrow Singlet–Triplet Energy Gap Sensitizer: a Simple Strategy for Efficient Visible‐Light Photochromism

Abstract All‐organic visible‐light photochromism is reported here via a novel strategy with narrow singlet–triplet energy gap (ΔE_ST) materials as a sensitizer. Taking advantage of the narrow ΔE_ST feature and the triplet–triplet energy transfer process, highly efficient photochromism of diarylethenes (DAEs) with both ring‐open and ring‐closure excitations shifted to visible light region is successfully achieved. Moreover, the wavelength of the visible excitation light can be easily modulated (e.g., from 405 to 470 nm) by elaborate selection of matched sensitized molecules. The “write‐and‐erase” application of this photochromic system in polymer films is further demonstrated. This strategy provides a simple and versatile selection of well‐matched DAE/sensitizer couples for visible‐light photochromism without complicated molecular design.