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.

Perovskite oxides (POs) are emerging as a class of highly efficient catalysts for reducing oxygen to H₂O. Although a rich variety of POs-based catalysts have been developed by tuning the complex composition, a highly efficient PO catalyst that is able to alter the reaction pathway from a 4e⁻ process to a 2e⁻ process for H₂O₂ production has rarely been achieved. We modified the structure and composition of a Ca- and Nb-based PO material by realizing a uniform two-dimensional (2D) morphology and varied Ta doping, resulting in the 2D Ca₂Nb_3−xTa_xO₁₀⁻ (x = 0, 0.5, 1, and 1.5) monolayer catalysts. The obtained catalysts exhibit a dominant 2e⁻ pathway and show exceptional H₂O₂ production efficiency. The typical Ca₂Nb_2.5Ta_0.5O₁₀⁻ nanoflakes showed an onset potential of 0.735 V vs. reversible hydrogen electrode (RHE), a remarkably high selectivity over 95% across a wide range of 0.3–0.7 V, an impressively high Faradaic efficiency of 94%, and a notable H₂O₂ productivity of 1571 mmol·g_cat⁻¹·h⁻¹. These findings highlight the great potential of 2D perovskite oxide nanoflakes as advanced electrocatalysts for 2e⁻ oxygen reduction reaction.