Si Wire-Array Photovoltaics and Hydrogen-Producing Photoelectrodes

ABSTRACT:

Si microwire arrays are three-dimensional semiconductor architectures which orthogonalize the directions of light absorption and carrier collection. This design, in principle, allows for the fabrication of efficient photovoltaics and fuel-generating photoelectrodes from relatively impure Si. Such wire arrays are grown by a vapor-liquid-solid-catalyzed process on a crystalline Si wafer lithographically patterned with an array of metal catalyst particles. Following growth, the wires can be embedded in plastic and peeled from the growth substrate yielding an unusual photovoltaic material: a bendable, wafer-thickness crystalline Si absorber.

In this colloquium I will describe:

1. the growth of high-electronic-quality Si microwires with controllable p-type doping and the evaluation of their solar energy-conversion performance using a test electrolyte that forms a rectifying conformal semiconductor-liquid contact
2. the fabrication and characterization of solid-state Si radial pn junctions based on this wire array platform
3. the integration of these arrays with hydrogen-evolving catalyst particles in order to directly drive the photocathodic reduction of water to hydrogen gas
4. efforts to achieve enhanced optical absorption in working, high-efficiency wirearray photovoltaic and photoelectrochemical devices.