Dual In Situ Synthesis and Nanopatterning of Ultrahigh‐Stability Perovskite Nanocrystals for Integrated Nanodevices

Manipulating perovskite nanocrystals (PNCs) with nanoscale patterning and structural integrity is critical for their integration into advanced optoelectronic devices. However, conventional patterning methods often compromise the structural integrity, detrimental to optical properties of PNCs. Here, a dual‐role strategy is reported that combines PNCs nanopatterning and in situ synthesis directly on versatile substrates, effectively circumventing the post‐synthesis processing damage. A complementary dual‐role mechanism, leveraging molecular coordination and network confinement, enables precise regulation over PNCs growth, yielding tunable crystallite sizes from 20 to 200 nm. Notably, the PNCs exhibit exceptional environmental stability, with photoluminescence intensity enhanced by approximately sixfold after 2000 h of exposure to ambient air. Furthermore, the fabrication of light‐emitting nanocrystal gratings using nanoimprint lithography is demonstrated, achieving sub‐40 nm resolution, precise alignment accuracy, and high aspect ratios, faithfully reproducing the predefined surface morphologies. Tunable optical responses are realized by customizing the PNCs array geometry, thus facilitating amplified directional radiation for sophisticated nanophotonic and optoelectronic applications. These findings establish a robust platform for integrated nano‐optoelectronics, opening avenues for advanced photonic devices and quantum optical applications.