Light trapping and reflection control in solar cells using tilted crystallographic surface textures

Surface textures made of <111> crystallographically oriented facets are examined for their capacity to enhance absorption and reduce reflection in solar cells. Some that employ microstructures with their axes of symmetry tilted from the surface normal can almost eliminate broadband top surface reflection and enhance the pathlength of weakly absorbed radiation as well as any schemes previously suggested. For example, tilting the axes of upright pyramids by about 24° towards the same base corner is estimated to enhance absorption of the solar spectrum in a 280 μm cell by up to 4.5%. Practical issues concerning the fabrication of “tilted” structures and suitability for reducing back surface losses are also discussed.