Study on the Plasma Texturing for Increasing the Conversion Efficiency of a Solar Cell with a DC Arc Plasmatron

摘要

A novel arc plasma source with a very low anode erosion rate (～40~(-10) g/C), a spectrally clean plasma flow and a lifetime of 10~3～10~4 hours, was developed. A texturing process was performed on a crystalline silicon (c-Si) wafer to increase the efficiency of a solar cell. A pyramid shape was etched on the wafer's surface by using a high durability DC arc plasma source at atmospheric pressure and low pressure. CF_4 and SF_6 were used as the reactive etching gases at flow rates <100 seem, with O_2 as the supporting gas in the range of the 5 - 15%. To survey the characteristics of the pyramid formation process, plasma texturing experiments were performed by varying the working time. The optimal operating conditions of the gas flow (Ar, O_2, CF_4, SF_6), plasmatron current and processing time were determined. The pyramid angle was approximately 50° to 60° when a single-crystalline silicon surface was textured in a vacuum whereas it was approximately 75° to 90° when textured at atmospheric pressure. The pyramid angle is related to the reflectance. The reflectance decreases with decreasing pyramid angle. The reflectance of the bare silicon ranged from 40% to the 60% but that of the textured silicon was approximately 5% to 20%. This reflectance is quite low, approximately half that reported by other studies using wet and Reactive ion etching (RIE) texturing. These results confirm that this novel arc plasma source can be used to texture a Si surface for applications to photo-voltaic devices.