Konferensartikel

Recently new advance texturing is one of the candidates for enchaining optical absorption in mono crystalline thin film solar cells and making low cost solar cell. Silicon has relatively large reflection in Uvvisible spectral region; also absorbs strongly in this region; however; its near IR absorption is weak. The absorption enhancement can occur through diffractive scattering from surface with feature dimension larger than ?/n; where n is silicon refractive index. For surface feature with size smaller than ?/n; surface is behaving like a gradient index film. By creating three-dimensional surface with sub wavelength textures on front and sidewalls; it may be possible to enhance absorption beyond the 4n² statistical limit. There is an idea that says implantation process during fabrication process affect solar cell efficiency because of p-n junction dependence to temperature. This maybe complicated the efficiency prediction. Since Because of difficulty of laboratory test and fabrication the simulation of implantation temperature method is considered for a well know three dimensional texturing at first. Simulations in first step are done for an ideal three dimensional surface texturing with 21µm depth and an ideal p-n junction below 1µm under frontal surface. In this simulation the p-n junction has a constant depth all over the solar cell. Then by using implantation modeling tries to predict the p-n junction place by varying the temperature all over the surface. It is shown that the p-n junction position and its shape completely depend on the temperature that causes a variety of efficiency for a well known advanced texture. In this case the p-n junction shows a discontinuity at 700 ºC that case an efficiency drop for 21% to 10%. These simulations confirm the impact of implantation temperature on optical simulation. Results are shown to find out the best design for advance three-dimensional texturing need to predict discontinuity temperature in fabrication process. Simulations also show the dependence of efficiency with geometrical surface features and how discontinuity temperature change by shape and size of the periodic texture pattern. Results show there is a limitation in final performance of mono-crystalline solar cell with periodic texture pattern.

Renewable energy; solar cells; thin film; surface texturing