Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Applied Physics | en_US |
| dc.contributor.advisor | Lau, S. P. (AP) | en_US |
| dc.creator | Liu, Duanzijing | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13595 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Polarization-sensitive photodetectors based on hybrid organic-inorganic perovskites | en_US |
| dcterms.abstract | Polarization-sensitive photodetectors are garnering significant attention due to their applications in medical science, bio-signal detection, astronomy, display technology, and quantum computing. They can be divided into linearly-polarized-light (LPL) photodetector and circularly-polarized-light (CPL) photodetector. Organic-inorganic hybrid perovskites (HOIPs), a group of materials characterized by their high absorption coefficients and long carrier diffusion lengths, are promising candidates for both LPL photodetectors and CPL photodetectors. LPL photodetectors based on HOIPs can be realized by using HOIPs with intrinsically anisotropic crystal structures or by combining HOIPs with other materials that have anisotropic crystal structures into heterojunctions, or by forming perovskites with anisotropic morphology, such as nanowires (NWs). However, synthesizing large-scale and high-quality HOIP crystals with an anisotropy crystal structure is challenging and time-consuming. Fabricating HOIP NWs also requires complex techniques. Additionally, the optoelectronic performance of LPL photodetectors requires further enhancement. CPL HOIP photodetectors are typically built on chiral HOIPs, which exhibit CPL-sensitive optical absorption and efficient charge carrier transport. Research on chiral HOIPs for photodetectors has focused on one-dimensional (1D) and two-dimensional (2D) chiral HOIPs, which feature relatively wide bandgaps. However, materials with tunable bandgaps and broad response regions are preferred for photodetectors. While significant efforts have been made to investigate chiral HOIPs with tunable bandgaps, materials that offer a broad response region and exceptional photoelectric properties still need further exploration. | en_US |
| dcterms.abstract | In this thesis, first, we fabricated an LPL photodetector based on nanoimprinted quasi-2D HOIP thin films with vertical gradient phase distribution. The nanoimprinting method is utilized to create nanoscale linear patterns on the surface of the film. It enables polarized light detection and enhances absorption. According to the results of transient absorption analysis, a vertical gradient phase distribution along the longitudinal direction of quasi-2D HOIP (PEA)2(MA)n-1PbnI3n+1 (PEA+ =C6H5CH2CH2NH3+, MA+ = CH3NH3+, n = 3) is confirmed, which facilitates efficient carrier transfer and separation, leading to improved device performance. These detectors demonstrate outstanding photo-response with a large responsivity of ≈90 A/W and a high detectivity reaching the order of 1012 Jones. The photoluminescence of the quasi-2D HOIP film exhibits an anisotropy ratio of 2.05, and the LPL photodetector reaches a polarization sensitivity of 1.68. These findings offer insight into the feasibility of developing HOIP materials for photodetectors, which have potential applications in imaging, sensing, and communication technologies. | en_US |
| dcterms.abstract | Second, we prepared chiral HOIP films with a wide distribution of multiple quasi-2D phases to achieve broadband CPL photodetectors. The chiral ligands S/R-MBA (S/R-MBA=S/R-methylbenzylammonium, C6H5CH(CH3)NH2) introduced chirality into the HOIP films. We encountered challenges obtaining quasi-2D phases within (S-MBA)2MAn-1PbnI3n+1 films, as the n=1 phase and the three-dimensional (3D) phase consistently predominated. However, when both PEA and S/R-MBA were introduced in the film, the (S/R-MBAxPEA1-x)2MA2Pb3I10 films exhibited multiple quasi-2D phases and demonstrated CD signals in a broad range. We investigated the optoelectronic performance of photodetectors based on (S/R-MBAxPEA1-x)2MA2Pb3I10 films with varying ligand ratios and successfully fabricated a CPL photodetector using the (R-MBAxPEA1-x)2MA2Pb3I10 film. This photodetector shows a broadband photo-response and achieves a high responsivity of 1.07 A/W under 0.742 mW/cm2 illumination at 447 nm. Additionally, it exhibits CPL sensitivity over a wide wavelength range. The anisotropy factor of photocurrents (gIph) under 447 nm, 532 nm, and 633 nm CPL illumination was measured to be 0.11, 0.19, and 0.10, respectively. | en_US |
| dcterms.abstract | Third, we synthesized chiral quasi-2D HOIP crystals, specifically (S/R-MBA0.4PEA0.6)2MAn-1PbnI3n+1 with n=1, 2, and 3. We characterized and compared these crystals' chiroptical and photoelectric properties with varying quantum well thicknesses. The crystals with n = 1, 2, and 3 were fabricated into CPL photodetectors, achieving anisotropic factors of 0.18, 0.28, and 0.16 under 520 nm, 532 nm, and 633 nm illumination, respectively. This work provides insights into the components of the (S/R-MBA0.4PEA0.6)2MAn-1PbnI3n+1 films discussed in Chapter 4 and introduces a new design strategy for chiral multilayered HOIPs in the field of CPL detection. | en_US |
| dcterms.extent | x, 136 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.LCSH | Optical detectors | en_US |
| dcterms.LCSH | Hybrid perovskites | en_US |
| dcterms.LCSH | Hong Kong Polytechnic University -- Dissertations | en_US |
| dcterms.accessRights | open access | en_US |
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