Synthesis And Photoluminescence Property Of Heteroiunction Consisting Of Two-dimensional Molybdenum Disulfide And PTCDA Organic Semiconductor

Group-VI transition metal chalcogenides,which has graphemep-like structure,is a new kind of two dimentional layered material and is attracting extensive attentions due to its excellent optical,electrical and catalytical properties.The properties render them the potential candidates for next-generation optoelectronic devices.However,the controllable synthesis for two-dimensional materials with better morphology and larger size is the prerequisite for their applications.Some preliminary results already proved that the reaction parameters have significant effect on the morphology of the two-dimensional material.In this essay,we aim to further study the effect of different reaction parameters on the preparation of two-dimensional molybdenum disulfide(MoS2).Combination of different materials to form a heterojunction can make up for the lack of a single material and obtain synergistic complementary effect.Heterojunctions built from organic semiconductors and two-dimensional materials have been attracting enormous attentions due to the extraordinary optical and electronic properties.Some works have been reported to combine some the organic semiconductors with two-dimensional MoS2.However,there are few reports on the photoluminescnec(PL)properties of the heteroj unction of TMDs and organic semiconductors.Therefore,it is necessary to study the changes of PL properties of heterojunction.In chapter one,we introduced the basic properties and the preparation methods of 2D group-VI transition metal chalcogenides.And then we reviewed the applications of the heterojunctions which were consisting of 2D materials and organic semiconductors.In chapter two,we changed the concentration of sulfur vapour and the synthesis temperature in the synthesis process to explore the effect on monolayer MoS2 which have different morphology,such as triangular star,triangular,hexagonal and nanobelts.Combining Auger electron spectroscopy(AES)and Raman spectra,it was suggested that the formation of MoS2 nanobelts mainly includes the formation of molybdenum dioxide nanowires and surface vulcanization.In chapter three,we reported the construction of van der Waals(vdW)heteroj unction by simply depositing organic semiconductor of 3,4,9,10-perylene tetracarboxylic dianhydride(PTCDA)onto two-dimensional(2D)MoS2 monolayer and grapheme respectively.And Raman and PL properties were characterized.We observe an enhanced photoluminescence(PL)intensity and PL peak shift of the MoS2/PTCDA heterojunction as compared with the solo MoS2 and PTCDA layer and a decreased photoluminescence(PL)intensity of the Graphene/PTCDA heterojunction.By using X-ray diffraction(XRD),Ultroviolet Photoelectron Spectrometer(UPS)and density functional theory(DFT),an enhanced photoluminescence(PL)intensity of the MoS2/PTCDA heterojunction as compared with the solo MoS2 and PTCDA layer is attributed to the improved crystallinity of the PTCDA on the MoS2 and the hybridization interaction between the MoS2 and the PTCDA.In contrast,the graphene/PTCDA heterojunction shows a reduced PL intensity due to the charge transfer from the PTCDA to graphene.