Research On Manipulation Of Localized Surface Plasmon Resonance By Graphene-Metal Nanoparticles

With the development of the world’s industrialization,the demand for energy is increasing.The current global energy consumption is still based on fossil fuels,which is not in line with the goal of sustainable development.As a representative of clean energy,organic solar cells(OSCs)have become a research hotspot because of the advantages of low cost,flexibility and large area fabrication.The active layer of OSCs devices is usually composed of organic semiconductor materials with low carrier mobility.In order to ensure that the photogenerated carriers can be effectively separated and collected by the electrode,the thickness of the active layer in OSCs is usually controlled at tens of nanometers,however,the ultrathin active layer cannot absorb enough sunlight.By introducing micro-nano structures inside OSCs devices,the photoelectric conversion efficiency of OSCs can be effectively improved.The structural parameters of the micro-nano structures play an important role in trapping photons at the desired wavelength range.Metal nanoparticles(NPs)are widely used in sensing,biomedical and optoelectronic devices because of their large specific surface area and their localized surface plasmon resonance(LSPR)effects.The LSPR supported by metal NPs with a strongly enhanced localized field can be applied in OSCs to improve light absorption at the resonant wavelengths.On the other hand,graphene has wide applications in OSCs due to its excellent optical and electrical properties.In addition,the hybrid structure of graphene and metal NPs can enhance the light-matter interaction.Therefore,how to excite a tunable LSPR is a key point to explore the application of graphene and metal NPs in OSCs.This thesis focused on the preparation of metal NPs,alloy NPs,and hybrid structure of graphene and metal NPs.The excited LSPR has been manipulated by controlling the size of metal NPs,the components of alloy NPs and graphene.The main work can be summarized as following:1.Metal NPs with homogeneous shape and uniform distribution were prepared,and the LSPR absorption peak was modulated by changing the size of the metal NPs.As the thickness of the thermally deposited Cu film increased from 5 nm to 20 nm,the diameter of the annealed Cu NPs increased from about 50 nm to about 200 nm,and the Cu NPs exhibited a red-shifted LSPR absorption peak from 561 nm to 576 nm.Similarly,the LSPR absorption peaks of Ag NPs exhibit a red shift from 412 nm to569.5 nm with increasing sizes of Ag NPs.2.Ag-Cu composite NPs(Ag&Cu NPs)and Ag-Au alloy NPs(Ag Au NPs)with different component ratios were prepared,and the LSPR absorption peaks were tuned by changing the component.The Ag&Cu NPs exhibit two discrete LSPR peaks in the absorption spectrum,which are more suitable for enhancing the light absorption in broadband wavelength range.In contrast,Ag Au NPs have only one LSPR peak,demonstrating the formation of alloy NPs.Resonance absorption peaks produced by Ag Au NPs with molar ratios of Ag1Au0,Ag3Au1,Ag1Au1,Ag1Au3,and Ag0Au1 are413 nm,429 nm,444.5 nm,484.5 nm,530.5 nm,exhibiting a red shift with the increasing molar ratio of Au.3.High quality graphene films and graphene/metal NPs hybrid structures were prepared to further tune the LSPR.By introducing a monolayer graphene,the absorption peaks associated with LSPR supported by NPs showed small red shifts.