The spectral responses of photovoltaic devices based on metal/porous silicon (PS)/silicon (Si) sandwich structures are presented. At room temperature, the photoresponse (photovoltage or photocurrent) of the devices has been measured by the variation of the optical excitation energy from a synchrotron radiation source from the near UV to the near IR. The highest photosensitivity was found to be around a wavelength of similar to 500 nm, corresponding to the maximum intensity of the solar spectrum. Having a wider photoresponse full width at half maximum (FWHM) than conventional forms of silicon used for solar cells within the earlier excitation energy range, PS has promising potential for enhanced photosensitivity efficiency. Such improvements could be made by modification of the Si nanostructure, since the peak position and FWHM were found to correlate with the size and size distributions of the pores, respectively, of the Si nanocrystallites in the porous Si layers. Gains could also be made in the contact design, and in any case such devices are more stable than their light emitting diode analogues. (C) 2000 American Institute of Physics. [S0021-8979(00)02907-8].