Humidity‐Assisted High‐Resolution Laser Patterning of Perovskite Nanocrystals on Glass Beyond the Diffraction Limit

Abstract Luminescent micro‐patterns of perovskite nanocrystals in glass written by femtosecond laser offer a novel alternative for integrated optoelectronic applications such as μ‐LED, image sensors, and optical communication. However, improving the resolution, specifically, reducing the sizes of pixel dots, of luminescent perovskite patterns directly processed by femtosecond laser in glass remains challenging due to the optical diffraction limit and the crystallographic nature of perovskites in glass. Herein, high‐resolution luminescent patterning is reported (with diameters of luminescent dots down to nanometer scale, beyond the diffraction limit) of perovskite nanocrystals on glass surfaces assisted by humidity treatment. The generation of photoluminescence (PL) emission from laser‐written non‐luminescent dot patterns is recognized as originating from the H 2 O‐promoted nanocrystallization of perovskites in the local region of pattern dots. By manipulating the humidity level or halide stoichiometry, arbitrary patterns with tunable emission colors can be fabricated. The current luminescent patterning strategy expanded practical applications in anti‐counterfeiting, information encryption/decryption, and optical storage. This work provides a high‐quality and versatile route toward high‐resolution perovskite patterns, which would unlock more new applications in optics and optoelectronics.