The Study Of The Optical Properties Of Surface Texture For Silicon Solar Cell

Bulk silicon solar cell still has an average reflectance up to10%, and the Yablonovitch limit of ultra-thin film solar cell is also difficult to surpass. This article will focus on how to overcoming these difficulties on silicon material by simply making surface microstructure.The solar cells is more sensitive to cost of manufacture and surface recombination, so after considering a large number of structures, the author suggest that a good solar cell surface micro-structure should meet the three criteria together: High absorption rate, low cost, low surface area. According to these three criteria we think that only nanowire structures and pyramid structure meet the above requirements, and therefore these two structures will use as research primitives.And we will introduce this work by two parts:In theory.1. Any periodic structure will have different optical phenomena vary with the cycle. This clearly defined the boundaries of the three optical theory range: range of the effective medium theory, P<n/λo;diffraction mode range,n/λo< 5λ0/ns,the light trapping achieve the best results.2. Within the scope of the effective refractive index theory,we further subdivided the applicable zone for two commonly used two-dimensional analytical EMT formula.When period is larger2/3(1/ns+ni sinθ)<p/λ0≤1/ns+nisinθ,Bruggeman formula will be quite right as me filling factor satisfy,0<FF<0.4or FF>0.8.when period is smaller1/3(1/ns+nisin θ)<P/λ0<2/3(1/ns+nisin θ),Maxwell-Garnett formula is very accurate as FF<0.8.In optimization.1. For bulk silicon solar cells:When the pyramid period is586nm and dense arranged,the weighted reflectivity is lower to5.2%,which is half of the current pyramid reflectivity.when design nanowire antireflection layer with h=200nm on the surface of micron pyramid structure,we get weighted reflection1.5%.2. For ultra-thin film solar cell witll thickness only2um:Double pyramid surface structure solar cell achieves the best short-circuit current density37.6mA/cm2.This value is equal to1.9times the planar silicon thin-film solar cell with the same thickness.This not only exceeds the Yablonovitch limit of such thickness,which is,33.2mA/Cm2,but also reached to86%of the short-circuit current density of Blackbody absorption.