| Author: | Liu, Qi |
| Title: | Chiral halide perovskite for multimodal chiroptoelectronics |
| Advisors: | Li, Mingjie (AP) Yu, Siu Fung (AP) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Department: | Department of Applied Physics |
| Pages: | xviii, 127 pages : color illustrations |
| Language: | English |
| Abstract: | Chirality refers to an intrinsic geometric property of an object that possesses non-superimposable mirror-image forms. Notably, chirality gives rise to a spectrum of unique photophysical phenomena, including nonlinear optical responses, chiral-induced spin selectivity, circular dichroism (CD), circularly polarized photoluminescence (PL), and spin-polarized exciton dynamics. The synergistic integration of chirality into halide perovskite yields chiral halide perovskites (CHPs), which manifest enhanced chiroptical-electronic properties by combining the spin-selective transport characteristics of chiral systems with the exceptional optoelectronic performance inherent to halide perovskites. In this thesis, CHPs with different morphologies (e.g., film, nanowire, and quantum well structure) are employed as functional layers to develop high-performance chiroptoelectronics, such as circularly polarized light (CPL) PAS and spin devices. Firstly, a heterostructure device composed of helical 1D chiral perovskite (H-PVK) and single-wall carbon nanotubes (SWNTs) is presented for circular polarization sensing PAS. The device exhibits excellent polarization sensitivity and photoresponsivity, which could be attributed to the strong light-matter interactions between H-PVK and SWNTs. With the aid of femtosecond pump-probe spectroscopy, we demonstrated the trapping of electrons in H-PVK and the effective collection of holes in the SWNTs. Such carrier dynamics contribute to a series of bioinspired circular polarization-sensitive neuromorphic behaviors including polarization-perceptual excitatory postsynaptic current, paired-pulse facilitation, and learning-forgetting-memory process. In application, a 7 × 7 device array is developed to show the potential application of the PAS in constructing an anti-glare neuromorphic vision system. It is shown that the perception and memory of the circular polarization states can be easily realized through modulating CPL with different spatiotemporal information. More importantly, PAS-based spike neural networks are simulated, and show a high recognition accuracy up to 90% under the advanced encoding way of PAS. The proposed PAS indicates a significant breakthrough toward the next-generation intelligent visual perception systems. Secondly, we propose a chiral perovskite nanowire-based heterostructure to achieve linear and circular polarization sensitive all-in-one PAS device. The designed PAS device exhibits high CD (400 mdeg) from chiral materials and intrinsic linear dichroism from nanowire morphology, enabling the full-Stokes detection. The PAS exhibits a longer carrier lifetime owing to efficient hole transfer from perovskite nanowire to MXene, which is demonstrated by TA, thereby contributing to a high responsivity (2.2 AW⁻¹) and excellent synaptic behavior (i.e., short-term plasticity, long-term potentiation). More importantly, the PAS device-based reservoir computing is performed and exhibits good prediction (NRMSE = 0.023) in the chaotic system forecasting task. This work provides an innovative design for achieving all-in-one neuromorphic sensing functions of linear and circular polarization, paving the way for the development of advanced visual systems that are capable of polarization-dependent perception. Thirdly, the quantum well structured CHP superlattice is synthesized and transferred to different substrates for study. Utilizing the micro-area absorption measurement equipment, an ultra-high CD value (>4000 mdeg) is demonstrated. The edge state of the superlattice structure that extremely enlarges the vertical carrier transport ability of the CHP is verified by the PL mapping. Moreover, an obvious current difference is observed between the vertical and planar direction, supporting the vertical transport preference. High spin polarization degree up to 90% is measured by the magnetic conductive atomic force microscope, which underlies the foundation for high-performance spintronics. This work designs a high-quality quantum well-structured CHP superlattice, paving the way for high-density spin memory and spin logic devices. In summary, this thesis supplies systematic exploration on CHPs for CPL-resolved PAS and spintronic devices, and extends the applicability of CHPs, demonstrating the potential of CHPs for next-generation chiroptoelectronics. |
| Rights: | All rights reserved |
| Access: | open access |
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