Electronic interactions of silicon nanocrystals and nanocarbon materials: Hybrid solar cells

Hybrid inorganic/nanocarbon solar cells represent low-cost solutions for the large-scale manufacturing of energy conversion devices. Here we discuss results that relate to the electronic interactions of nanocarbon materials with freestanding and surfactant-free silicon nanocrystals (Si-ncs) with quantum confinement effects, integrated in bulk-heterojunction solar cells. In particular, we demonstrate the feasibility of bulk-heterojunction photovoltaic solar cells that consist of Si-ncs combined with fullerenes or with semiconducting single-walled carbon nanotubes (SWCNTs). We show that the energy levels between Si-ncs with energy gap exceeding 1.75 eV and fullerenes are adequate for exciton dissociation and carriers (electrons/holes) generation and that hybrid solar cells formed by Si-ncs and semi-conducting SWCNTs favor exciton dissociation only when a distinct chiral index [i.e., (7,5)] is used. While fullerenes show energy conversion capabilities in the visible spectral region (1.7–3.1 eV), the cells containing the SWCNTs, in comparison, have a considerably expanded optical response covering a broad range of the spectrum (0.9–3.1 eV).