Precision engineering chiral interfaces for efficient spin injection in metal halide heterostructures

Precise control of interfaces is crucial for spin generation, transport, and detection in opto-spintronics. However, the interface engineering for efficient spin injection remains a significant challenge. Here, we synthesized a helical structure of PbI₂ (R-PbI₂) via an interfacial chirality-induced growth approach at the heterostructure interface. This few-nanometer-thick R-PbI₂ layer shows a lower lattice mismatch with both the adjacent R-NEAPbI₃ (R-NEA refers to R-1-(1-naphtyl)ethylamine) and PbI₂ layers, and leads to an optimal chiral interface in the chiral heterostructure with minimized residual strain and defect density. Combined with circularly polarized pump-probe spectroscopic and spin-photovoltaic measurements, our chiral heterostructure interface contributes a spin-injection efficiency up to 68%, thus leading to a degree of polarization of 29% in photocurrent. The precise synthesis of a chiral interface offers a promising route to manipulate spin dynamics and achieve a high degree of spin polarization required for advanced opto-spintronic applications.