Graphene-Templated Achiral Hybrid Perovskite for Circularly Polarized Light Sensing

This study points out the importance of the templating effect in hybrid organic-inorganic perovskite semiconductors grown on graphene. By combining two achiral materials, we report the formation of a chiral composite heterostructure with electronic band splitting. The effect is observed through circularly polarized light emission and detection in a graphene/α-CH(NH₂)₂PbI₃ perovskite composite, at ambient temperature and without a magnetic field. We exploit the spin-charge conversion by introducing an unbalanced spin population through polarized light that gives rise to a spin photoconductive effect rationalized by Rashba-type coupling. The prepared composite heterostructure exhibits a circularly polarized photoluminescence anisotropy g_CPL of ∼0.35 at ∼2.54 × 10³ W cm^-2 confocal power density of 532 nm excitation. A carefully engineered interface between the graphene and the perovskite thin film enhances the Rashba field and generates the built-in electric field responsible for photocurrent, yielding a photoresponsivity of ∼10⁵ A W^-1 under ∼0.08 μW cm^-2 fluence of visible light photons. The maximum photocurrent anisotropy factor g_ph is ∼0.51 under ∼0.16 μW cm^-2 irradiance. The work sheds light on the photophysical properties of graphene/perovskite composite heterostructures, finding them to be a promising candidate for developing miniaturized spin-photonic devices.