Photoactive silicon-based nanostructure by self-organized electrochemical processing

A solar cell design is presented that allows energy conversion in solid-state photovoltaics as well as in photoelectrochemical and photoelectrocatalytic cells. The energy-converting structure uses a Schottky-type, (i. e., metallic) nanoemitter, prepared by an oscillatory (photo) electrochemical process. Silicon shows (photo) current oscillations in fluoride-containing electrolytes that form an oxide with interspersed nanopores. Spatially selective electrodeposition of Schottky-barrier metals into these pores produces the nanoemitter contacts. The n-Si/SiO2/Pt/redox electrolyte structure shows pronounced photoactivity in a photoelectrochemical cell. Light-induced hydrogen evolution is obtained for structures made with p-Si. The energy-band alignments of the structures are discussed and routes for preparation of efficient solid-state devices are outlined. (c) 2007 The Electrochemical Society.