Scattering property of rough surface of silicon solar cells

1. ISAPE 2010 Guangzhou, China PAPER NO***** Scattering property of rough surface of silicon solar cells Bai Lu a, b,* ,Wu Zhensen a , Tang Shuangqing a and Pan Yongqiang b a School of Science, Xidian University, Xi’an 710071, China bSchool of Opto-electronic Engineering, Xi’an technological university 710032, China ABSTRACT In this paper, the correlations properties of silicon solar cells are measured, the nanoscale roughness surface high fluctuation coordinate function distribution is obtained, based on the Kirchhoff approximates method the numerical results of this material are presented. The correlation between the coherent and the incoherent scattering intesities along with the incident or the scattering angle are also discussed. Keyword: Rough surface; Scattering ; Kirchhoff approach method Introduction THEORETICAL FOUNDATION The electric field of the incident and scattered wave is given by Light scattering Properties of material surface topography and micro rough surface measurements are becoming increasingly important in many applications. A great variety of science and engineering disciplines have significant interest in scattering of light and other electromagnetic radiation by randomly micro rough material surface for many years. In order to meet the increasing requirements of high quality optical coating components, the reduction of scattering losses has become essential. Hence, deeper insight into the mechanisms causing light scattering in dielectric thin films is necessary. In this paper, the correlations properties of some special micro rough surfaces are measured, the nanoscale roughness surface high fluctuation coordinate function distribution is obtained, based on the Kirchhoff approximates method the numerical results of this material are presented. The correlation between the coherent and the incoherent scattering coefficients along with the scattering angle are discussed. (1) (2) the Fresnel reflection coefficients perpendicular and parallel polarized component (3) (4) the bistatic scattering coefficients can be decomposed into a coherent part and the incoherent part (5) (6) (7) Results and discussion Figure 1 gives a general schematic diagram of an instrument used for performing surface profile measurements. The apparatus can be divided into three parts: the source, the sample holder and the data analytical system. The source is composed of white light source. In order that the beam incident upon the sample have as good a beam profile as possible ,the beam is filtered with a lens and beam splitter. The object to be measured is place on a sample holder. the test sample materials is silicon solar cell, the length of the sample is 8mm, it’s roughness surface profile and the surface profile measurement results are illustrated in Fig.2 and Fig.3. The profile curve in Fig.3 is a special cross-section of the sample illustrated in Fig.2. All the height position function coordinate could be obtained and the data file could be saved. As we assume that the surface height function is single valued and has zero mean, the statistical characteristic are validated to satisfy the Gaussian distribution. Through multiple sample check statistically, the root-mean-square height and the correlation length of the sample could be acquired. According to the definition, when the value fall to of the maximum value of y-coordinate then the corresponding x-coordinate is the correlation length, as showed in Fig.4. In Fig.5 The coherent scattering intensity various with the incident angle are shown. In this numerical computation, the results are obtained as the local angle Fresnel reflection coefficient is for perpendicular polarization. Where case1 the scattering angle and the azimuth angle are 30 degree. In case2 both angle are 45 degree and in case3 both angle are 60 degree. From the Fig.5 we can see the coherent components only contribute in the specular reflected directions. For the different case the peak value almost corresponding the different specular reflected case. the sample could be viewed as almost a flat surface. The scattered intensity includes more specularly reflected coherent intensities. Conclusion In this article, we use the white light interference surface talysurf to survey the silicon solar cells material with naro scale roughness surface. The nanoscale roughness surface high fluctuation coordinate function distribution is obtained by the three-dimensional surface measurement data. The statistical characteristic is obtained. And based on the Kirchhoff approximates method, the numerical results of this material are presented. The computation results showed that the rough surface statistical parameters of different material will remarkably influence its diffusion properties. All this results have significant contributions to the research of how to reduce the reflects losses and improve its Conversion efficiency. School of Science, xidian university, Xi’an 710071, China , blu@xidian.edu.cn