Preparation Of CdS Nanosheet Array Structure And Its Applications In Optoelectronics

Owing to its excellent photoelectric properties,CdS nanostructures are widely utilized and exhibit good performances in visible light optoelectronic devices,such as photodetectors,solar cells,light-assisted gas detectors,photo-electrochemical(PEC)hydrogen generation cells and photocatalyst devices.Due to that the characters of devices are strongly dependent on the qualities of materials and the architectures of devices,we therefore concentrate the research of this thesis on the growth of CdS nanostructures and the design and fabrication of related optoelectronic devices with high performance.In chapter one,we first discussed briefly the principle of optoelectronic device.Then we summarized several typical growth methods for CdS nanostructures and their applications in the optoelectronics.Finally,we presented the research focus and key results of this thesis.In chapter two,we developed chemical bath deposition(CBD)method into nanostructure growth and fabricated CdS nanosheet arrays(NSAs)with a facile,fast and low-cost CBD method.The morphology,structure and photoluminescence of CdS NSAs were systematically investigated and the zinc blende structure with good crystal quality of NSAs was revealed.Moreover,it was found that the growth of CdS NSAs with CBD method is independent of the substrate,demonstrating the universality of the method.By changing the concentrations of precursors or the growth time,we studied the underlying mechanism of the growth and found that the formation and decomposition of complexes may play an important role during the growth of NSAs.In chapter three,we first discussed the effect of photodetector configuration on its performance and then fabricated a vertical photodetector based on CdS NSAs.The characterization of this photodetector was carried out and the excellent overall photoresponse of the device to the light was found.Specially,at the bias voltage of 10 V and under the irradiation of 440 nm light with 1.1 mW/cm2 power density,the photodetector showed an high on-off ratio of?100,responsivity of 629A/W and specific detectivity of 1.4×10,3 Jones.The cause of integrated high performance of the device were discussed and attributed to the enhanced light absorption of NSAs structure as well as the facilitating collection of light-generated carriers through the vertical configuration.Finally,we proposed simply possible ways to further enhance the photoresponse of CdS NSAs based photodetector.In chapter four,we applied CdS NSAs as a photoanode in the photo-electrochemical cell(PEC)for hydrogen generation.Some preliminary characterization on the photoanode in PEC system were presented.It is found that,under 5 mW irradiation of 632 nm light,the saturated current density of the device reached as high as the magnitude of 1 mA/cm2,demonstrating its potential in practical applications.Additionally,the effects of surface modification on CdS NSAs photoanode by TiO2,Al2O3 and Nafion were also investigated,and the results implied that the inner defections in CdS NSAs is possibly the dominantly important factors of its performance.As a consequence,improving crystal quality and decreasing the inner defections of CdS NSAs may be the effective way to further enhance the performance of the photoanode.