Composite Of Sb₂S₃ Microrods And PbI₂ Nanoflakes And Their Photodetection Properties

With an optical band gap between 1.5 and 2.2 e V,antimony sulfide（Sb₂S₃）is non-toxic,earth abundant,environmentally friendly with a high light absorption coefficient.In recent years it has been widely used in photovoltaic cells,photocatalysis,energy storage and photodetectors.Sb₂S₃ microrods（MRs）have a direct band gap（E_g～1.61e V）and the photodetector based on Sb₂S₃ MR has a light response in the 550-750 nm,but with a low response rate.As a two-dimensional material,lead iodide nanoflakes（Pb I₂ NFs）have a band gap of 2.34 e V.Pb I₂ NF has a high photoresponsivity in the410-500 nm,with a narrow spectral response range and limited detection capability toward visible light.Therefore,combining Sb₂S₃ MR and Pb I₂ NF to form a hybrid device can not only broaden the light response of Pb I₂ NF in the visible light range,exhibiting a broadband spectral response from 400 to 750 nm,but also enhance the photoresponsivity and effectively improve the optoelectronic properties of Sb₂S₃ MR and Pb I₂ NF.In this thesis,photodetectors based on Sb₂S₃ MR,Pb I₂ NF and Pb I₂NF/Sb₂S₃ MR were respectively prepared,characterized and analyzed to unravel their morphology,structure,optical properties,and photoelectric properties.The main contents and results are briefly summarized as follows:First,Sb₂S₃ MRs with high purity,crystallinity and low defect density were successfully prepared by a combination of hydrothermal and post-annealing processes,and characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and X-ray diffraction analyses.Next,the optical properties were systematically analyzed using ultraviolet visible absorption（UV-vis）spectra,Raman and photoluminescence（PL）spectroscopy.Finally,the optoelectronic properties of the Sb₂S₃ MR photodetector were tested using a Keithley 4200 device.The Sb₂S₃ MR photoelectric device manifests a response rate of 6.38 A/W,external quantum efficiency（EQE）of 1.11×10³%,and detection rate of 2.7×10¹⁰ Jones.Next,Pb I₂ NFs were successfully prepared by a simple recrystallisation method and its morphology was characterized by SEM.The results showed that the Pb I₂ NF prepared by this method was hexagonal in shape with a clean,smooth surface and clear edges.Next,the structure and composition of the samples were analyzed by energy dispersive X-ray spectrum（EDX）and X-ray diffraction（XRD）.The results showed that the Pb I₂ NFs were well crystalline,phase-pure and free from impurities.Then,the optical properties of the nanoflakes were characterized using UV-vis and Raman spectroscopy.Finally,the Pb I₂ NF was prepared into photodetector for optoelectronic performance test.The results showed that the Pb I₂ NF photodetector has a good photo-selectivity with a switching ratio of 2.8×10³,a response rate of 9.30 A/W,an EQE of2.58×10³%and a detection rate of 3.64×10¹² Jones under 445 nm monochromatic illumination.Then,Sb₂S₃ MR was successfully transferred onto Pb I₂ NF to form a composite structure using a two-dimensional material transfer platform.Morphological and compositional analyses of Pb I₂ NF/Sb₂S₃ MR were carried out using SEM and EDX.The optical properties of the Pb I₂ NF/Sb₂S₃ MR structure were characterized by Raman spectroscopy.Finally,the Pb I₂ NF/Sb₂S₃ MR-based optoelectronic device was fabricated and its optoelectronic properties were investigated.The results showed that compared with the Pb I₂ NF device,the Pb I₂ NF/Sb₂S₃ MR composite device has a response rate of 155.67 A/W,an EQE of 4.36×10⁴%and a detection rate of 3.16×10¹³Jones under 445 nm monochromatic illumination.Compared with the Sb₂S₃ MR device,the Pb I₂ NF/Sb₂S₃ MR composite device has a response rate of 120.74 A/W,an EQE of 2.06×10⁴%and a detection rate of 2.45×10¹² Jones under 730 nm monochromatic illumination.This paper focuses on photodetectors based on Sb₂S₃ MR and Pb I₂ NF,and compares the performance of single Sb₂S₃ MR and Pb I₂ NF photodetectors with Pb I₂NF/Sb₂S₃ MR composite photodetector.It is found that the Pb I₂ NF/Sb₂S₃ MR composite device has a wider band spectral response than the single Sb₂S₃ MR and Pb I₂NF.In addition,the TypeⅡenergy band structure of the composite materials can effectively promote the separation of electron-hole,resulting in a significant increase in the responsivity,EQE and detection rate of the composite device.