Excitation-Wavelength-Controlled Spin Injection in Core-Shell Chiral Perovskite Nanocrystals for Amplified Circularly...

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 MAPbI₃ 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 MAPbI₃ 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.