Contrasting photovoltaic response and photoluminescence for distinct porous silicon pore structures

The photoluminescent (PL) emission and photovoltaic (PV) response of two di stinctly structured (prepared) porous silicon (PS) surfaces are compared an d contrasted. The PV response of a porous silicon structure consisting of a microporous framework on which is superimposed a nanoporous layer is disti nct from that of the branched nanoporous silicon structure generated in an aqueous etch environment. The observed PV response for this hybrid morpholo gy is clearly not dominated by the covering nanoporous structure and displa ys a response that appears to be intermediate between those observed for na noporous PS (band gap 1.80 +/- 0.2 eV) and crystalline: silicon. In contras t, rime-dependent histograms of the PL emission from the hybrid microporous -nanoporous and nanoporous structures, although not precisely the same, are quite similar. These observations, while consistent with a surface-dominat ed emission process associated with a bound fluorophor and not with the qua ntum confinement model, do suggest the influence of the PS bulk morphology on surface transformation.