Carrier multiplication in nanoparticle PbSe/single crystal Si heterojunctions

Abstract

Nanoparticle PbSe/single crystal Si heterojunctions, prepared by a chemical bath deposition technique, show enhancement in forward and reverse currents in I–V characteristics under visible light illumination. The increase in current can be attributed to carrier multiplication by Auger electron emission and/or direct generation of multiexcitons. Photochromatic sensitivity, which is nearly the same under 425 nm and 675 nm illumination for 72 nm PbSe (bulk)/Si heterojunctions, is a sensitive function of incident wavelength and size in the smaller grain size (<30 nm) film heterojunctions. 9 nm PbSe/Si heterojunctions, preferentially, are blue sensitive whereas 26 nm heterojunctions are more sensitive to red light. The selectivity is mainly due to the variation in band gap in PbSe films with grain size. The studies project the heterojunctions as interesting candidates for photovoltaic investigations.