Synthesis Of Quantum Dots/Graphene Nanocomposites And Its Application On Enhanced Photoelectric Response Device

With the development of science and technology,the technology of photoelectric detection has been widely used in our daily life,for example,the intelligence of emergency alarm such as smoke detection and fire detection,public lighting switch,and automatically adjustable switch for the devices such as laptops.Currently,the commonly used photoelectric detection technologies mainly based on materials such as CdS、CdSe、CdTe、Si、Ge.However,there are many defects for these materials such as the complex synthesis process;the high cost;the restriction of the size;the worse cooling performance and the the bottleneck of the running speed.Therefore,with the development of technology,it becomes more and more urgent to search for new alternative materials.In recent years,researchers began to develop new materials,explore new mechanisms and design new structures to study new and efficient optoelectronic devices.So far,the materials which were used for photoelectric device mainly focus on organic fluorescent molecules,metal complexes and organic semiconductor materials.Specially,semiconductor materials have been widely used in the photoelectric detection devices due to their high quantum efficiency and structure stability.On the other side,graphene showed potential application prospect in the field of photoelectric detection due to its high conductivity,excellent mechanical properties and large specific surface area.In recent years,many researchers combined graphene and semiconductor materials to prepare graphene based nanocomposites,which exhibited improved photoelectric response speed and responsivity.Additionally,perovskite nanomaterials also have great application prospect in the field of photoelectric detection because of its high carrier mobility of the carriers,longer diffusion length,excellent visible light absorption ability,solution processing approach,and wavelength tunable excellent photoelectric properties.In this thesis,we used the AgInZnS quantum dots,perovskite quantum dot materials and graphene to prepare QDs/RGO nanocomposites,and the pure perovskite nanorods were further studied.The performance of the photoelectric devices based on QDs/RGO nanocomposites,perovskites have been deeply analysised and studied,in view of the excellent performance of these materials and devices,we have done the following research works:In the first chapter,we reviewed the structure,properties and synthesis methods of graphene,semiconductor nanomaterials and perovskite nanomaterials,clarified the research significance of this thesis.The corresponding research progress in domestic and oversea for the photoelectric detectors has been summarized.Moreover,we analyzed the methods for preparing semiconductor nanomaterials/graphene nanocomposites and perovskite nanomaterials,and introduced the important significance of this thesis.In the second chapter,the preparation methods of AgInZnS nanoparticles,reduced graphene oxide(RGO)and AgIn ZnS/RGO nanocomposites are introduced.The properties of the above materials were characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD),absorption spectroscopy(Abs)and fluorescence spectroscopy(PL).In order to study its optical properties,we prepared a photoelectric detection device based on AgInZnS/RGO nanocomposites.The experimental results show that the photoelectric device based on the nanocomposites has a relatively high photocurrent switching ratio of 210%,the responsivity is 1mA/W,and the rise time of photocurrent is 0.62 s,and the down time is 0.29 s.The third chapter introduces the synthesis methods of pure CsPbBr3 nanoparticles and CsPbBr3/RGO nanocomposites,after summaried up the various synthesis methods of perovskite nanomaterials,the hot-injection method was employed for preparing CsPbBr3 nanoparticles and CsPbBr3/RGO nanocomposites.The morphology,structure feature and optical properties were tested and characterized.In order to investigate the photoelectric response of the obtained CsPbBr3/RGO nanocomposites,a simple photodetector device was fabricated by dropping the CsPbBr3/RGO nanocomposites which dissolved in toluene onto a gold interdigital electrode on SiO2 substrate with a 20 μm spacing between the adjacent fingers.Also the photoelectric properties were tested,the photocurrent switch ratio is 170% and the responsivity is 16.2mA/W,the rise time is 0.41 s,and the fall time is 0.42 s.The fourth chapter introduces the preparation methods of one-dimensional inorganic perovskite CsPb(Br/I)3 nanostructure,the reaction parameters including reaction time,temperature and composition have been studied,to achieve a high production rate of CsPb(Br/I)3 nanorods preparation.The structure,morphology and optical properties of CsPb(Br/I)3 nanorods were tested and characterized.In order to study the performance of photodetector,a simple photodetector device was fabricated by dropping the CsPbBr3/RGO nanocomposites which dissolved in toluene onto a gold interdigital electrode on SiO2 substrate with a 3 μm spacing between the adjacent fingers,the photocurrent switch ratio is 200000%,the responsivity is is 187.5mA/W,when there is light,the rise time is 0.68 s,and the fall time is 0.66 s.In the fifth chapter,the research work of this paper is summarized,the advantages of the above materials and the photoelectric detectors based on the above materials,and the development of the photodetector based on the new materials is prospected.