| The photovoltaic energy industry has been developed rapidly in recent years,and solar cells are the most important part of photovoltaic energy technology.Silicon-based solar cells occupy an important position in the solar cell market due to their advantages such as stable performance,high efficiency,and abundant raw materials.Due to the presence of Fresnel reflection,bare monocrystalline silicon will reflect about 30%of the sunlight when it is used on the surface of solar cells,resulting in a low utilization rate of light energy.Therefore,studying how to improve the silicon-based solar cells conversion efficiency has important engineering application values.The usage of silicon surface microstructures to achieve anti-reflection has become a research hotspot in this field in recent years,and the anti-reflection characteristics of surface microstructures are closely related to microstructure parameters.Therefore,on the basis of clarifying the visible light reflection characteristics of different types of textures on the silicon surface,the optimal design of surface microstructures to further reduce the surface reflection loss is the fundamental way to improve the photoelectric conversion efficiency of silicon-based solar cells.Based on this,the common visible light(400-800 THz)reflection characteristics of three types of simple microstructures are investated,and the relationship between the reflection characteristics for different types of surface microstructures to different frequency bands of visible light are summarized.On this basis,a design scheme of surface microstructure to achieve visible light reduction of silicon-based thin films is proposed.The paper mainly carried out the following works:(1)The reflection characteristics of six kinds of surface convex microstructures(cones,cylinders,truncated cones,quadrangular pyramids,quadrangular prisms,and quadrangular pyramids)to visible light were systematically studied,and the shape and size of the convex structures and their visible light reflection characteristics were analyzed.The relationship between:the cross section of the pyramid and the prism in the height direction is gradient,and the prism is the same cross section in the height direction.Pyramid-shaped and pyramid-shaped surface convex microstructures have the best duty ratio f=1,the best period is T=200 nm,and the best height H=800 nm.The optimal duty ratio of the micro structure of the prismatic convex surface is inverse f=0.7,the optimal period is 200 nm,and the effect of height change on the reflectance reduction is not obvious.During the combination,four types of surface convex microstructures with a gradient cross section,cone,truncated cone,quadrangular pyramid and quadrangular pyramid,are combined in two pairs.For the combined composite convex surface microstructure,the reflectivity is lower than that of a single.The convex micro structure on the surface shows that it is advisable to reduce the reflectivity in a combined manner.The lowest average reflectance of combination is 4.7%.(2)The reflection characteristics of six kinds of surface depression microstructures(cone,cylinder,truncated cone,quadrangular pyramid,quadrangular prism,and quadrangular pyramid)to visible light were systematically studied,and the relationship between the shape and size of the concave structure and its visible light reflection characteristics was analyzed.Relationship:The longitudinal cross-section of the pyramid and bevel is a gradient cross-section,and the longitudinal cross-section of the prism is an equal cross-section.Pyramid and truncated pyramidal surface depression microstructures have the best duty cycle f=1,the best period is T=400nm,and the best height H=800nm.The optimal duty ratio f=1 of the concave prismatic surface microstructure,the optimal period T=400nm,the influence of the height on the reflectivity is fluctuating,the micro structure of the cylindrical concave surface reaches the lowest reflectivity when the height is equal to 500nm,quadrangular prismatic The concave surface micro structure reaches the lowest reflectivity when the height is equal to 600nm.When combining,the surface depression structure with a gradient cross section such as a circular truncated cone and a quadrangular pyramid is cross-combined with the surface depression micro structure such as a cylindrical and quadrangular prism.For the combined composite surface depression microstructure,the reflectivity Both are lower than the micro structure of a single convex surface,which shows that it is advisable to reduce the reflectance by combination.The lowest average reflectance of combination is 7.9%.(3)Based on the results of the previous two parts,according to the principle of complementary performance,four types of composite surface microstructures were designed and their reflection characteristics were studied:the prism-shaped concave surface microstructures with equal cross-sections and the pyramids and prism-shaped protrusions with gradient cross-sections were selected Starting from the surface microstructure,it is finally combined into four new composite surface microstructures of cylindrical depression round platform protrusion,quadrangular prism depression quadrangular pyramid protrusion,quadrangular prism depression quadrangular pyramid.When f=0.5,the average reflectivity of the combined composite surface micro structure has been significantly reduced.For example,the average reflectivity of cylindrical depressions is 35.7%,and the average reflectivity of conical protrusions is 43.4%.The average reflectance dropped to 13.4%,indicating that the combined anti-reflection is better than before the combination.When f=1.0,the average reflectivity of the combination of cylindrical depression conical protrusion and quadrangular prism depression pyramid combination is better than before combination,but the average reflectance of combination of cylindrical depression conical protrusion and quadrangular prism depression quadrangular protrusion is higher than Before the combination,it shows that when f=1.0,the cylindrical concave circular truncated projections and the quadrangular prismatic concave truncated pyramidal projections are not suitable for the combined composite surface micro structure.Among them,when f=1,T=400nm,H=800nm,the average reflectivity of the cylindrical concave conical convex is lower than other combinations,6.8%,which is the optimal structure.Through the above research,it can be found that a reasonable combination of single surface microstructures can further reduce the reflectivity.Among them,the lowest average reflectivity of the combination of quadrangular pyramidal protrusions and circular truncated protrusions is 4.7%.The lowest average reflectance after combined with cylindrical depression is 7.9%,and the lowest average reflectance after combined with cylindrical depression and conical protrusion is 6.8%.The results obtained in this paper have a certain reference value for further research on the anti-reflection of surface microstructures in the future,and provide some new ideas for the diversified design of surface microstructures. |
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