Combining ligand-induced quantum-confined stark effect with type II heterojunction bilayer structure in CdTe and CdSe nanocrystal-based solar cells

We show that it is possible to combine several charge generation strategies in a single device structure, the performance of which benefits from all methods used. Exploiting the inherent type II heterojunction between layered structures of CdSe and CdTe colloidal quantum dots, we systematically study different ways of combining such nanocrystals of different size and surface chemistry and with different linking agents in a bilayer solar cell configuration. We demonstrate the beneficial use of two distinctly different sizes of NCs not only to improve the solar spectrum matching but also to reduce exciton binding energy, allowing their efficient dissociation at the interface. We further make use of the ligand-induced quantum-confined Stark effect in order to enhance charge generation and, hence, overall efficiency of nanocrystal-based solar cells. © 2012 American Chemical Society.