2D/3D Heterostructured Perovskites for Highly Selective Room-Temperature Blue Spin-Polarized Light-Emitting Diodes

Circularly polarized light can be utilized in numerous applications, including 3D displays and magnetic memory. In this study, pure-blue spin-polarized light-emitting diodes (spin-LEDs) were fabricated by depositing chirality-induced spin selectivity (CISS) layers—2D perovskites incorporating R / S -2-fluoromethylbenzylamine ( R / S -2F-MBA) chiral cations—on top of Br/Cl mixed-halide 3D perovskite thin films. The chiroptical properties of these heterostructured perovskites were significantly improved, as reflected in an approximately six-fold increase in circular dichroism over a conventional iodide perovskite. Density functional theory calculations indicated that as the ionic radius of the halogen atom decreased relative to that of iodine, the hydrogen bonding between the ammonium groups of the chiral cations and the halide anions in the inorganic slabs became stronger; this facilitated a chirality transfer from the 2F-MBA to the inorganic slabs and amplified the structural distortion. Halogen–halogen interactions contributed further to this chirality transfer, improving the spin-polarizability of the CISS layer. The significantly enhanced CISS effect yielded pure-blue spin-LEDs with a circularly polarized electroluminescence dissymmetry factor exceeding 10%. Additionally, the highly polar R / S -2F-MBA chiral cations effectively passivated halide vacancies in the perovskite film, boosting luminescence as well as external quantum efficiency. As a preliminary proof of concept, the spin-LEDs were employed as vertical-type circularly polarized light photodetectors, enabling interactive optical wireless communication.