Preparation And Surface Plasmon Properties Of Silver/Tin Core/shell Nanocomposites

In the field of silicon-based thin film solar cells,the heterogeneous electronic structures between noble metals and Si will result in some electronic defects which will be harmful to the performance of devices.Therefore,Ag/Sn core/shell nanostructures formed by wrapping metallic Sn with group IV nature on Ag with best surface plasmon resonance could be a promising candidate to enhance the light absorption performance of Si-based solar cells.In this dissertation,the surface plasmon properties of nano-Ag,nano-Ag dimer and nano metallic Sn(?-Sn)were respectively studied firstly.Based on the results,the research on the preparation and surface plasmon performance of Ag/Sn core/shell nanostructures had been carried out.In details,Ag/Sn core/shell nanostructures had been synthetized by a wet chemical method,and the corresponding surface plasmon properties had been characterized.On the basis of above results,the enhancement of absorption of Si thin film embedded with different nanoparticles had been explored.The detailed research results are as below:1.The size-dependent and incident angle-dependent surface plasmon performance of Ag nanoparticle and Ag nano-dimer have been studied by using a finite element method.The simulated results indicate that the size-dependent surface plasmon performance are agree with the conventional Mie theory,implying that the high-order resonance modes will appear with the increasing of the size of nanoparticles,and the bigger nanoparticles are,the lower resonance frequency will get.In addition,the average near-field enhancement factor of Ag nano-dimer will reach the maximum of 10⁶ orders of magnitude,which is 3 orders higher than that of a single Ag nanoparticle,when the gap is 0 nm and the light incident perpendicularly to the long axis of the dimer.2.Well-crystallized?-Sn nanoparticles with different sizes have been prepared by a wet chemical method at different reaction temperatures.Both optical characterizations and finite element simulations confirmed that the size-dependent surface plasmon performance of?-Sn reveal the same variation trend with Ag case,namely,the high-order resonance modes will appear with the increasing of the size of nanoparticles,and the bigger nanoparticles are,the lower resonance frequency will get.In addition,the calculation indicates that the maximum near-field enhancement factor under excitation of 600 nm,which is 44,can be reached when the particle size is 100 nm;while the corresponding surface-enhanced Raman scattering experiments of R6G with the concentration of 10^-3 reveal that the maximum enhancement factor is 1.3.3.Ag/Sn core/shell nanostructures by water bath and polyol method,respectively.The optical measurements reveal that the existence of?-Sn could dramatically broaden the surface plasmon frequency range of 200-1200 nm,although the wrapping of?-Sn will quench the light emission from Ag due to the strong interaction between Ag and?-Sn.Meanwhile,the finite element simulations determined the critical coupling distance between Ag and?-Sn is around 3.4 nm.Furthermore,the simulations regarding the Si thin film with embedding nanoparticles indicate that Ag/Sn core/shell nanostructures have stronger enhancement effect in the range of 700-1200 nm for Si than the Ag or?-Sn nanoparticles when the embedding depth is 40 nm.