Silicon Nanowire Array Photoelectrochemical Cells

Abstract

Silicon nanowire arrays were grown by vapor−liquid−solid growth from SiH4 vapor at 500 °C, and tested as photocathodes in [Ru(bpy)3]2+ (bpy = 2,2'-bipyridyl)/acetonitrile solutions. Si nanowires were grown in anodic aluminum oxide membranes by first electroplating 50 μm long Co wires capped with 250 nm gold segments in the pores and then reacting with SiH4. The resulting Si nanowires protruded 10−15 μm beyond the top surface of the membrane but were degeneratively doped, most likely by Al from the membrane. Nanowires grown in the same manner on Si(111)/Au substrates could be controllably doped p-type by addition of trimethylboron. These p-Si nanowire arrays gave a photovoltage of 220 mV in [Ru(bpy)3]2+ solution when illuminated by white light.