Experimental study of rectangular groove texture in the surface of photovoltaic silicon with diamond coated micro-milling tools

Abstract

Microstructure in the surface of photovoltaic silicon can decrease the reflectance of light and improve absorption efficiency of silicon solar cell, and mechanical texturization is a kind of clean method to fabricate light trap microstructure in the surface of silicon. This paper is an experimental study to verify reflectance simulation of rectangular groove texture in the surface of photovoltaic silicon. In this paper, two types of micro-end diamond coated cemented carbide tools in different diameters were used to carry out mechanical texturization in single crystal silicon along <111> and <100> crystal orientation. Firstly, formulas aiming to achieve ductile mode milling are derived and offering guidelines for subsequent parameters set of rectangular light trap machining, and then cutting parameters such as axial depth of cut, feed rate and uncut width (width of wall between adjacent rectangular grooves) were studied for diamond different coated tools. The finish and integrity of structures obtained by machining along < 111 > and < 100 > crystal orientations were compared and analyzed, and machining along < 100 > crystal orientation showed a better surface finish and integrity of light trap than along < 111 > under the same conditions. Finally, the appearance of worn tools were observed and the reflectance of fabricated light trap microstructure was analyzed, and a satisfying reflectance below 15% for 0.4–1.1 µm wavelength lights can be achieved in the texture obtained when the principle angle of light incidence > 20°.