Improving The Performance Of Multi-crystalline Silicon Solar Cells By Localized Plasmonic Effect Of Ag Nanoparticles

Metallic nanoparticles,especially noble nanoparticles,are widely used in optics,electronics,biology,industrial catalysis and many other fields.It is well known that metallic nanoparticles present great potential for trapping more lights into solar cells due to localized surface plasmonic resonance(LSPR)effect.Under sunlight irradiation,the LSPR can be excited by the congregate oscillations of the free electron cloud of metallic atoms,and exhibits optical and electromagnetic enhancement depending largely on the metal's size,shape,arrangement and dielectric environment.Recent years,metal-catalyzed chemical etching(MCCE)technology has been widely applied in mass production of multi-crystalline silicon solar cells(mc-Si).On this basis,it is vital to further optimize the MCCE technology while to incorporate the plasmonic effect of metallic nanoparticles into silicon solar cells for better performance.The main research of this paper is as follows:Firstly,a textured submicron structure(800-1100 nanometers in diameter and 500-700 nanometers in depth)was fabricated on the silicon surface via MCCE technology and Ag nanoparticles were deposited on the silicon substrate by means of thermal evaporation method.The morphology,spacing and optical performance of Ag-NPs could be manipulated by optimizing the parameters of deposition time,annealing temperature and etcSecondly,Ag-NPs array was embedded in the SiNx passivation layer of full-sized mc-Si solar cells(size of 156×156x 0.150 mm3,resistivity of 1-3 ? cm).The optical and electrical properties of the cells have been investigated by manipulating various parameters,such as the morphology,the average diameters of Ag-NPs and the depth of Ag-NPs array embedded in the SiNx passivation layer.When the depth of Ag-NPs array was 25 nm and the optimal deposition time was about 40s,the best experimental result was obtained:open-circuit voltage(Voe)increased from 623.2 mV to 627.6 mV(~4 mV higher),energy conversion efficiency(ECE)increased from 18.05%to 18.25%.Eventually,a physical model of Si/SiNx/Ag-NPs composite structure was established,and its LSPR effect was simulated by the commercial software Comsol 4.3a.After calculation,the results indicate that the UV resonance absorption was existed in wavelength range of 350-550 nm while the long wave forward-scattering enhancement was appeared in wavelength range of 550-1100 nm.The simulation results are in good agreement with the experimental conclusion,which provide useful guidance for the subsequent parameter optimization.In summary,the performance of conventional silicon solar cells can be improved by the LSPR effect of Ag-NPs.On the one hand,the cells have a certain optical loss in short wavelengths near the plasmonic resonance frequency of Ag-NPs,but their open circuit voltages and fill factors are increased due to depressed surface recombination as those short wavelength photons are mainly absorbed by Ag-NPs instead of the surface.On the other hand,the cells show strong absorption in long wavelengths,which can be attributed to the forward-scattering effect of Ag-NPs.Taking together,the cell efficiency can be increased from 18.05%to 18.25%embedding with proper Ag-NPs.The techniques presented in this work can be easily incorporated into the current mc-Si solar cell production line,thus have great potential for the mass practical application.