Molecular Design of Chiral Low-Dimensional Perovskites with Amplified Chirality and Carrier Mobility for Direct Circularly Polarized Light Detection
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Circularly polarized light (CPL) photodetectors are critical for applications in quantum information, spin-optical communication, and remote sensing, owing to their ability to distinguish the handedness of CPL-encoded spin information. Current CPL detection technologies rely on conventional photodetectors integrated with linear polarizers and quarter-wave plates, which increase system complexity, cost, and reduce sensitivity. Chiral low-dimensional perovskites have emerged as promising materials for CPL photodetectors. However, selectively detecting left-handed and right-handed circularly polarized (LCP/RCP) light remains challenging due to their limited chirality and charge carrier mobility. To tackle these challenges, this study combines molecular design and device engineering in a synergistic approach to amplify the chirality and charge transport of chiral low-dimensional perovskites for highly selective and sensitive CPL detection. We first mix chiral aryl (R)-(+), (S)-(-)-α-methylbenzylammonium (R, S-MBA) and achiral alkyl n-butylammonium (nBA) cations in the organic layer. The resulting 2D (R, S-MBA0.5nBA0.5)2PbI4 perovskites exhibit a tenfold enhancement in chirality compared to (R, S-MBA)2PbI4 perovskites, attributed to enhanced asymmetric hydrogen-bonding interactions between the organic and inorganic layers, and hence a greater octahedral distortion. The photodiode-typed CPL photodetectors fabricated with (R, S-MBA0.5nBA0.5)2PbI4 display a self-powered capability with distinguishability, gres, of -0.58 and 0.54 at 0 V bias, respectively, setting new benchmarks among chiral 2D perovskite-based CPL detectors. To improve charge transport and tune band alignment between the organic spacers and inorganic frameworks, we design and synthesize chiral n-type naphthalenediimide (NDI)-based cations, (R)-NDIEPA+. The resulting chiral 1D (R-NDIEPA)PbI3 perovskites show a strong chiroptical activity. Moreover, they demonstrate a type II band alignment that facilitates charge separation with ultrafast charge transfer across the interface of the [PbI6]4- inorganic chain and the (R)-NDIEPA+ cation. Additionally, doping 1 - 10 mol % (R)-NDIEPA+ into chiral 1D (R-MBA)PbI3 improves both chiroptical activity and carrier mobility compared to pristine (R-MBA)PbI3. The chiroptical activity of pristine and doped (R-MBA)PbI3 and performance of photodiode-typed CPL photodetectors fabricated with chiral 1D (R-MBA)PbI3/PbI2 heterostructures show a clear trend with the crystallinity of the perovskites. Our work presents a rational design framework to tailor the chiroptical activity and electronic property of chiral perovskites, advancing the development of highly sensitive and selective CPL photodetectors.