Two-dimensional nonlayered CuInSe₂ flakes with in-plane polarization for self-powered broadband Schottky photodetectors

Ultrathin nonlayered chalcopyrite semiconductors provide an unique platform for integrating strong light-matter interactions, asymmetric crystal fields, and intrinsic defect engineering into high-performance optoelectronic devices. However, the device implementation has been hindered by controlled materials synthesis and reliable contact engineering. Herein, we demonstrate a molecular sieve-assisted chemical vapor deposition (CVD) strategy for the bottom-up growth of highly-crystalline two-dimensional (2D) CuInSe₂ flakes with well-defined (112) facet orientation and periodic Cu vacancy ordering. Comprehensive structural and spectroscopic characterizations reveal that the ordered cation sublattice breaks inversion symmetry, producing spontaneous in-plane polarization that can be electrically modulated via Cu⁺ ion migration. Coupled with a selected Au/CuInSe₂ Schottky contact, the intrinsic p-type conduction of 2D CuInSe₂ is verified, and the combined effects of polarization and junction fields enable efficient photocarrier separation and extraction under zero bias. The resulting self-powered photodetectors exhibit broadband operation across 450–1064 nm, with high responsivity of 0.6 A/W, detectivity of 2.97 × 10¹⁰ Jones, and external quantum efficiency of 119% under 637 nm illumination. Furthermore, the devices deliver a peak power conversion efficiency of 10.4% and a rapid photoresponse time of 85–103 ms. These results establish 2D chalcopyrite semiconductors as a versatile platform for next-generation energy-efficient optoelectronic technologies.