Excitation‐Wavelength‐Controlled Spin Injection in Core–Shell Chiral Perovskite Nanocrystals for Amplified Circularly Polarized Luminescence

ABSTRACT Chiral perovskites enable spin‐polarized light emission through the chiral‐induced spin selectivity (CISS) effect, offering a pathway toward magnet‐free spin‐optoelectronic devices. However, in most CISS‐based luminescent systems, the spin‐filtering and light‐emitting functions are intrinsically coupled, which obscures the independent role of spin injection in modulating emission and precludes a clear mechanistic understanding. Here, a core–shell chiral perovskite nanocrystal system consisting of an achiral MAPbI 3 core and a two‐dimensional chiral perovskite shell based on R / S ‐1‐(2‐naphthyl)ethylamine (NEA) is reported. This heterostructure enables excitation‐wavelength‐controlled spin injection. Owing to the strong absorption of the chiral shell at 375 nm and its transparency at 532 nm, 375 nm excitation activates a CISS‐mediated shell‐to‐core spin‐polarized carrier injection pathway, whereas 532 nm excitation mainly populates the MAPbI 3 core directly. This optical switching of the injection pathway boosts the circularly polarized luminescence (CPL) dissymmetry factor ( g lum ) from 1.5 × 10 −3 (532 nm excitation) to 3.8 × 10 −3 (375 nm excitation). In parallel, the magnetic conductive‐probe atomic force microscopy (mCP‐AFM) measurements reveal up to 85% spin polarization, and transient absorption spectroscopy shows a distinct 48 ps shell‐mediated population transfer component. These findings establish that CISS‐mediated spin injection can be optically controlled by excitation wavelength, enabling wavelength‐addressable spin manipulation in chiral heterostructures.