Lithography-less high-throughput manufacturing of anechoic silicon nanocone surface for antireflective solar wafer productions

Owing to the increasing demands for renewable energy in the new millennium, the development of higher efficiency and yet lower cost photovoltaic or solar cell devices is in more and more pressing needs today. The photon absorption rate in the solar spectrum directly affects the overall energy conversion efficiency of solar cells. Photon energy loss on the surface of solar cells is primarily due to the specular and/or diffuse reflection of the light. Anti-reflection coating is commonly used in current solar cell manufacturing in which multilayer dielectric film [1] or nanoparticle sludge [2] is commonly deposited on the silicon solar wafer surface. Not even mentioning the additional high cost associated with the coating process and material, most antireflection coatings are only effective in a relatively narrow spectrum range and may compromise the underlying devices [6]. Micro to sub-micron scale surface texturing or roughening by wet etch and optional photolithography [7] is also used in today's silicon solar wafer productions, however this expensive step cannot effectively eliminate diffuse reflection and may degrade wafer qualities. Recently various nanomaterial approaches were developed to enhance the optical absorption via creating nanostructures on solar cell surface which includes noble metal nanoplasmonics particles enhancing energy transfer [4] as well as periodical or random 3D nanostructures such as nanowire [8], nanopillar [5], and nanocone [9] arrays "trapping" photons on surface.