Chemical Vapor Deposition Growth of 2D Nonlayered CuInSe₂ for Vacancy‐Assisted Broadband Photodetection

The properties and device applications of 2D semiconductors are highly sensitive to intrinsic structural defects due to their ultrathin nature. CuInSe₂ (CIS) materials own excellent optoelectronic properties and ordered copper vacancies, making them widely applicable in photovoltaic and photodetection fields. However, the synthesis of 2D CIS nanoflakes remains challenging due to the nonlayered structure, multielement composition, and the competitive growth of various by-products, which further hinders the exploration of vacancy-related optoelectronic devices. Here, 2D CIS nanoflakes are successfully synthesized using a molecular sieve-assisted chemical vapor deposition process. The anisotropic van der Waals growth with well-defined exposed facets is closely associated with the presence of the molecular sieve. Electron microscopy techniques reveal the ordered copper vacancies within the as-grown 2D crystals, extending the optical absorption to the near-infrared region. Consequently, 2D CIS nanoflake-based photodetectors exhibit broadband photodetection capabilities (470 to 1550 nm) and exceptional performance, such as a high responsivity of 11 A W^-1, an external quantum efficiency (EQE) of 2143%, and a fast response speed of ≈46.5 ms under an incident wavelength of 637 nm, highlighting their promising potential in next-generation optoelectronics.