Graphene-Templated\nAchiral Hybrid Perovskite for Circularly\nPolarized Light Sensing

This study points\nout the importance of the templating effect in\nhybrid organic–inorganic perovskite semiconductors grown on\ngraphene. By combining two achiral materials, we report the formation\nof a chiral composite heterostructure with electronic band splitting.\nThe effect is observed through circularly polarized light emission\nand detection in a graphene/α–CH(NH<sub>2</sub>)<sub>2</sub>PbI<sub>3</sub> perovskite composite, at ambient temperature\nand without a magnetic field. We exploit the spin–charge conversion\nby introducing an unbalanced spin population through polarized light\nthat gives rise to a spin photoconductive effect rationalized by Rashba-type\ncoupling. The prepared composite heterostructure exhibits a circularly\npolarized photoluminescence anisotropy <i>g</i><sub>CPL</sub> of ∼0.35 at ∼2.54 × 10<sup>3</sup> W cm<sup>–2</sup> confocal power density of 532 nm excitation. A carefully engineered\ninterface between the graphene and the perovskite thin film enhances\nthe Rashba field and generates the built-in electric field responsible\nfor photocurrent, yielding a photoresponsivity of ∼10<sup>5</sup> A W<sup>–1</sup> under ∼0.08 μW cm<sup>–2</sup> fluence of visible light photons. The maximum photocurrent anisotropy\nfactor <i>g</i><sub>ph</sub> is ∼0.51 under ∼0.16\nμW cm<sup>–2</sup> irradiance. The work sheds light on\nthe photophysical properties of graphene/perovskite composite heterostructures,\nfinding them to be a promising candidate for developing miniaturized\nspin-photonic devices.