Study On Light Absorption Enhancement Structure Of Thin Film Silicon Solar Cells

At present,silicon solar cells still occupy 90%of the market,but the cost of silicon is still high because the thickness of commercial batteries on the market is still 170-180nm.Therefore,reducing material cost is one of the main ways to reduce the cost of photovoltaic devices.Thin-film silicon solar cells reduce the use of silicon materials but also bring new challenges.How to maintain the high efficiency of solar cells while reducing the thickness of the silicon layer.Efficient trapping structure can extend the optical path of light by scattering trapping,waveguide mode coupling,etc,and couples more incident light into the absorption layer to improve the absorption efficiency of the thin-crystalline silicon battery.In this paper,a new type of periodic positive dome structure is proposed innovatively.This structure is more efficient than conventional inverted pyramid structures,only a simple wet etching process is required,which is similar to inverted pyramid structures.The trapping principle of the structure is analyzed.At the same time,the high efficiency of the structure is theoretically explained by simulation.Then the trapping structure is successfully prepared by wet etching,and the excellent performance is verified experimentally.Finally,the structure is characterized on the hybrid solar cell to demonstrate its better light trapping ability than the pyramid.The main contents of our research are:Firstly,this thesis analyzes the trapping principle of pyramid and upright dome structure by ray tracing.The positive dome structure has four reflection regions compared with the pyramid structure,and the three reflection regions occupy a larger proportion than the pyramid.The structure's excellent light trapping ability has been initially demonstrated.Then,we optimized the periodic inverted pyramid structure,inverted nanoprism structure and the positive dome structure on thick silicon by rigorous coupled wave analysis(RCWA)to determine the optimal parameters of the structure.Then,we simulated the angular spectrum and short-circuit current density of three structures on 100um and 50um thick silicon.From the perspective of anti-reflection and light trapping,it is found that the upright dome structure has better absorption than inverted nanoprism structure and inverted pyramids.At 50 um silicon,the short-circuit current density of the periodic upright dome structure is still as high as37.5 mA/cm~2 at normal incidence.Then,we used the Mach-Zehnder laser interferometer and anisotropic etching to successfully prepare three trapping structures under optimal parameters on silicon.At the same time,in order to illustrate the light trapping ability of the structure on thin silicon,we used two ways to thin the structured silicon wafer to 100um and 50um,and measure the reflection of three structures at 0°,10°and 20°incident angles respectively.Finally,in order to explain the influence of the three structures on the electrical performance of the solar cells,we integrated three trapping structures with Si/PEDOT:PSS hybrid heterojunction solar cells to measure the electrical parameters of the battery.Finally,we found that the short-circuit current density of the upright dome structure is 0.78 mA/cm~2 higher than the pyramid structure,which fully demonstrates the superiority of this positive dome structure.