Appendix A: Comparison of ray-tracing with Birandy and Sunrays programs

Transcription

1 Comparison of ray-tracing with Birandy and Sunrays programs Appendix A: Comparison of ray-tracing with Birandy and Sunrays programs Comparison of ray-tracing programs Birandy and Sunrays In order to check the accuracy of ray-tracing using Birandy[1], the program was tested against Sunrays [2,3], a well established ray-tracing program used in the solar cell community, in addition to comparison to experimental data as was shown in Chapter 5. Polished silicon and silicon textured with periodic geometrical structures such as inverted pyramids and twodimensional V-shaped grooves, were modelled with both programs and the resulting absorption A, reflection R (with surface and total reflection represented by R s and R t respectively) curves and J sc (max) values compared. The cell structures used were as for Chapter 5, these being a) bare silicon in air, b) silicon in air with an Ag BSR, and c) silicon with 3mm glass + EVA front encapsulation and an intimate Ag BSR (see Figure 5.6). The results are shown in the following pages and are found to be in good agreement for the two ray-tracing programs. References [1] D. Thorp, S. R. Wenham, Ray-tracing of arbitrary surface textures for light-trapping in thin silicon solar cells, Solar Energy Materials and Solar Cells 48 (1997) [2] R. Brendel, SUNRAYS: A versatile ray tracing program for the photovoltaic community, in Proc. 12 th EPVSEC, Amsterdam (1994) [3] R. Brendel, SUNRAYS 1. Manual, Sunrays program and user manual, distributed by Garching Innovation GmbH 173

2 Appendix A a) Wafers in air (i) Lambertian ideal: planar silicon with front surface R = %, rear surface R = %, polished front, fully Lambertian rear. Silicon thickness = 186 µm J sc (max) from Birandy = ma/cm² J sc (max) from Sunrays = ma/cm² (ii) Double polished wafer, silicon thickness = 186 µm J sc (max) from Birandy = ma/cm² J sc (max) from Sunrays = 26.9 ma/cm² 174

3 Comparison of ray-tracing with Birandy and Sunrays programs a) Wafers in air (cont.) (iii) Perpendicular 2D V-shaped grooves (X-grooves on front surface, Y-grooves on rear), with facet tilt angles θ = Silicon thickness = µm J sc (max) from Birandy = ma/cm² J sc (max) from Sunrays = ma/cm² (iv) Front surface inverted pyramids with facet tilt angles θ = 54.7, polished rear. Silicon thickness = µm J sc (max) from Birandy = ma/cm² J sc (max) from Sunrays = 36. ma/cm² 175

4 Appendix A b) Wafers in air with intimate Ag BSR (i) Double polished wafer, silicon thickness = 186 µm J sc (max) from Birandy = ma/cm² J sc (max) from Sunrays = ma/cm² (ii) Front surface grooves with facet tilt angle θ = 35, silicon thickness = µm J sc (max) from Birandy = ma/cm² J sc (max) from Sunrays = ma/cm² 176

5 Comparison of ray-tracing with Birandy and Sunrays programs c) Wafers encapsulated with an intimate Ag BSR (i) Double polished wafer, silicon thickness = 186 µm J sc (max) from Birandy = ma/cm² J sc (max) from Sunrays = ma/cm² (ii) Front surface grooves with facet tilt angle θ = 35, silicon thickness = µm J sc (max) from Birandy =.53 ma/cm² J sc (max) from Sunrays =.96 ma/cm² 177

6 Appendix A c) Wafers encapsulated with an intimate Ag BSR (cont.) (i) Front surface inverted pyramids, facet tilt angles θ = 54.7, silicon thickness = 186 µm J sc (max) from Birandy = ma/cm² J sc (max) from Sunrays = ma/cm² 178