Study Of The Regulation Technique Of Pyramid On Single Crystal Silicon Surface

Photovoltaic is one of the important methods to tackle with the global energy crisis and the environment pollution. A lot of efforts have been focusing on the enhancement of the efficiency of the photoelectric conversion. One of the most important techniques in improve the conversion efficiency is to reduce the surface reflectance to absorb more light energy to generate more electron hole pairs. By using chemical etching, texturing "pyramid" structures can be formed on the silicon surface. These texturing "pyramid" can cause the secondary reflection and refraction of the light; therefore, more light illumination can be absorbed in the silicon based solar cells. By using the anisotropy etching principle, we can prepare the ideal "pyramid" structures with small size, uniform distribution and ideal morphology, and then low reflection of the silicon surface can be realized.According to the anisotropy etching principle, the article firstly qualitatively analyzes the causes of alkali-silica reaction; secondly, explores the methods to change the anisotropic etching properties; and thirdly investigates the techniques to regulate the size and distribution of "pyramid" structure. The article studies the effect of different solutions on the sizes and distributions of "pyramid" of single silicon. The experiment shows that when OH-concentration is1%and the concentration of C2H5OH is13.4%, the pyramid structure is the most appropriate, in which the sizes and distributions are in the best situation. The further investigation shows that C2H5OH has the function of reducing the rate of alkali-silica reaction and it can make the bubbles generated from the reaction departure from the silicon surface rapidly.This article further studies the influence of different surfactants on the anisotropic etching of alkali-silicon. By using SEM observation, we find that different surfactants and different contents can change the anisotropy etching properties. The experiments respectively studied the effects of alkali with surfactant, TMAH solution, and alkali with sodium silicate on the surface structures of single silicon. The experiments indicate that: firstly, the "pyramids" of alkali-silicon have different sizes and asymmetric distributions; secondly, TMAH solution can improve the reaction rate, but the "pyramid" structures have a disadvantage of different sizes and an asymmetric distribution; thirdly, the surfactant with alkali can etch the ideal "pyramid" structures, and the sizes are between1-4μm and the distribution is uniform, besides, the reflectivity of this structure is below12%. Therefore, it indicates that surfactant can not only change the anisotropic etching rate, but also can control the size and the morphology of textured "pyramids".