Spectral response of porous silicon based photovoltaic devices

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