Polarization Sensitive Hybrid Perovskite?CH₃NH₃PbI₃? Nanowire Photodetectors

The progress in photoelectric detection and imaging technology is affecting some key fields in the society,such as military affairs,communications and health care.Polarization detection introduces polarization as a physical quantity to increase the ability to collect information.The 3-dimensional space?light intensity,spectra and space?of light information then extends to a 7-dimensional space?light intensity,spectra,space,polarization grade,polarization angle,polarization ellipticity and rotation direction of the electric vector?.Polarization detection has a broad prospect applying in aspects like atmospheric detection,hydrologic detection and target recognition.As a hot material in optoelectric fields,hybrid perovskites have merits of large absorption coefficient and long carrier lifetime and are well applicable for high-quality thinfilm solar cells and photodetectors.Based on the knowledge and research progress in hybrid perovskites,our group explores and fabricates their nanostructures such as nanowires and quantum dots.On the basics,further material and physical characterizations are performed.The nanostructures are then used for the fabrication of polarization-sensitive photodetectors.This thesis is devoting to investigate the polarization performance of CH₃NH₃PbI₃ nanowire photodetectors.Self-assembly drop-coating method was first used to grow directionally aligned single-crystalline CH₃NH₃PbI₃ nanowire arrays.A series of material characterizations,such as ultraviolet visible spectrophotometer?UV-Vis?,X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,fluorescence spectrometer?PL?and Fourier transform infrared spectroscopy?FTIR?,were applied to analyze the structure,constitution,crystal quality,etc,and obtain its physical and chemical properties.Secondly,based on Finite-Difference Time-Domain?FDTD?theory,this thesis performed polarization-dependent optical simulations on CH₃NH₃PbI₃ nanowire.The results showcase how the photo-generated carriers change with the polarization angle and the size of nanowire and provided guidance for device design and test.Afterwards,parameters like spectral responsivity,response time,noise and normalized detectivity were measured on nanowire photodetectors.Oleic acid was successfully used to passivate nanowire surface defects.The optimized device has larger responsivity and detectivity.At last,we measured the polarized light current of the CH₃NH₃PbI₃ nanowire system.A satisfactory polarization performance is then obtained.