A hybrid heterojunction based on fullerenes and surfactant-free, self-assembled, closely packed silicon nanocrystals

We demonstrate that nanosecond-pulsed laser chemistry in water leads to closely packed and stable luminescent assemblies of silicon nanocrystals (SiNCs) that can be electronically coupled with fullerenes (C 60 ) without any additional surfactant or catalyst. We show that the fragmentation time in water determines the photoluminescence (PL) intensity (>40%) and redshifts the PL maxima (45 nm) of the SiNCs. Heterojunction solar cells made out of these laser-produced self-assemblies of SiNCs and C 60 show photovoltaic action with increased quantum efficiency in the region where the absorption of SiNCs appears.