Direct Detection\nof Near-Infrared Circularly Polarized\nLight via Precisely Designed Chiral Perovskite Heterostructures

Abstract

Chiral metal halide perovskites (CMHPs) have recently\nshown great\npotential for direct circularly polarized light (CPL) detection. However,\nowing to the limited cutoff wavelength edge of these CMHPs, most of\nthe detectors presented thus far are characterized only in the ultraviolet\nand visible range; CMHPs that target at the near-infrared (NIR) region\nare still greatly desired. Here, we design a novel CMHP heterostructure,\nsynthesized via solution-processed epitaxial growth of crystalline\n3D MAPbI₃ on a 2D chiral (<i>R</i>-BPEA)₂PbI₄ (<i>R</i>-BPEA = (<i>R</i>)-1-(4-bromophenyl)­ethylammonium) crystal, and provide the first\ndemonstration of self-powered direct NIR-CPL detection. Compared with\nindividual chiral (<i>R</i>-BPEA)₂PbI₄, the heterostructure not only retains the spin selectivity but also\nallows much broader absorbance, especially beyond 780 nm, where the\n(<i>R</i>-BPEA)₂PbI₄ cannot absorb.\nFurthermore, the built-in electric potential in the heterojunction\nforces spontaneous separation/transport of photogenerated carriers,\nenabling the fabrication of devices operating without external energy\nsupply. By making use of the abovementioned advantages, the self-powered\nCPL detectors of the (<i>R</i>-BPEA)₂PbI₄/MAPbI₃ heterostructures hence show competitive\ncircular polarization sensitivity at 785 nm with a high anisotropy\nfactor of up to 0.25. In addition, a large on/off switching ratio\nof ∼10⁵ and an impressive detectivity of ∼10¹⁰ Jones are also achieved. As a pioneer study, our results\nmay broaden the material scope for future chiroptical devices based\non CMHPs.