Direct Detection of Circularly Polarized Light Using Chiral Copper Chloride-Carbon Nanotube Heterostructures

The emergent properties of chiral organic-inorganic hybrid materials offer opportunities in spin-dependent optoelectronic devices. One of the most promising applications where spin, charge, and light are strongly coupled is circularly polarized light (CPL) detection. However, the performance of state-of-the-art CPL detectors using chiral hybrid metal halide semiconductors is still limited by the low anisotropy factor, poor conductivity, and limited photoresponsivity. Here, we synthesize 0D chiral copper chloride hybrids, templated by chiral methylbenzylammonium (R/S-MBA), i.e., (R-/S-MBA)₂CuCl₄, that display circular dichroism for the ligand-to-metal charge transfer transition with an absorption anisotropy factor (g_CD) among the largest reported for chiral metal halide semiconductor hybrids. To circumvent the poor conductivity of the unpercolated inorganic framework of this chiral absorber, we develop a direct CPL detector that utilizes a heterojunction between the chiral (MBA)₂CuCl₄ absorber layer and a semiconducting single-walled carbon nanotube (s-SWCNT) transport channel. Our chiral heterostructure shows high photoresponsivity of 452 A/W, a competitive anisotropy factor (g_res) of up to 0.21, a current response in microamperes, and low working voltage down to 0.01 V. Our results clearly demonstrate a useful strategy toward high-performance chiral optoelectronic devices, where a nanoscale heterostructure enables direct CPL detection even for highly insulating chiral materials.