Tailored Remote Photochromic Coloration of in situ Synthesized CdS Quantum Dot Loaded WO₃ Films

Abstract CdS quantum dot (QD) loaded WO₃ films, fabricated by screen printing and short‐time chemical bath deposition (CBD) techniques, have been proven to have an efficient visible‐light‐driven photochromic response. One of the striking features of such a photochromic system is its remote photochromic characteristic. The photogenerated electrons in CdS are injected into WO₃ to cause the color change of WO₃, while CdS does not show any photochromism. Compared to bare WO₃ films, the spectral sensitivity of remote photochromism in the CdS QD loaded WO₃ films is red‐shifted. The onset wavelength for remote, the decoloration time for CdS QD loaded WO₃ films was found to be significantly shorter than that for bare WO₃ films, probably due to their different electron trapping processes. Bandgap excitation in bare WO₃ creates deeply trapped electrons in the bulk, whereas the electrons injected from the QDs are trapped at shallow surface states in the remote photochromic system. The successful tailoring of photochromic coloration employing a simple procedure would provide numerous opportunities for designing photo‐ and electrochromic materials with the optimal architecture and tunable properties.