Truncated pyramid structures for see-through solar cells

1. A method for making a three-dimensional thin film solar cell, comprising:

patterning a reusable crystalline silicon template with a periodic array of hexagonal pyramidal cavities according to a wet chemical etching process, said reusable crystalline silicon template having dimensions of approximately 200×200 millimeters;

chemically cleaning said reusable crystalline silicon template;

forming a sacrificial porous silicon release layer comprising at least two different porosity values on a surface of said reusable crystalline silicon template, said porous silicon release layer comprising:

a top layer having a porosity in the range of 20% to 40%; and

a bottom layer having a porosity in the range of 40% to 80%;

depositing a doped crystalline silicon film onto said sacrificial porous silicon release layer, said doped silicon film being substantially conformal to said reusable crystalline silicon template and having a thickness in the range of 2 to 50 microns;

etching said sacrificial porous silicon release layer;

detaching and removing said doped silicon film from said reusable crystalline silicon template; and

removing a plurality of tips from said doped silicon film by:

depositing a hard masking thin layer having a thickness in the range of 0.05 to 0.5 microns on said doped silicon film;

patterning said hard masking thin layer according to a self-aligned selective chemical etching process, thereby creating exposed crystalline silicon regions not covered and protected by said hard masking layer; and

performing a selective silicon etching process to selectively etch away said regions not covered by said hard masking layer, thereby creating an array of see-through holes in said doped silicon film.