Ray-tracing of arbitrary surface textures for light-trapping in thin silicon solar cells

Abstract

A new ray-tracing program is introduced for modelling the anti-reflection and light-trapping properties of arbitrary surface textures. The validity of the ray-tracing model is discussed. The program is used to ray-trace thin crystalline silicon solar cells that might be deposited on to chemically etched glass. The scattering effectiveness of the textured surface is much greater by reflection than by transmission. Thus for best light-trapping properties (which might approach the lambertian ideal), the rear surface of the cell should be textured. Front surface reflection losses for a module under typical yearly averaged illumination conditions are, however, quite significant. A range of metal and detached reflectors are considered, and also bifacial modules. For a 10 μm thick film, a maximum J sc of 34–35 mA cm 2 seems likely under real conditions.