Multiple Exciton Generation in Quantum-Confined Semiconductor Nanostructures

Nanomaterials are a flexible material platform that has great promise for providing new ways to approach solar energy conversion. The synthesis, investigation, and utilization of these novel nanostructures lie at the interface between chemistry, physics, materials science and engineering. Semiconductor nanostructures, where at least one dimension is small enough to produce quantum confinement effects, provide new pathways for controlling energy flow and therefore have the potential to increase the efficiency of the primary photo conversion step. In this discussion, I will present the current status our research efforts towards utilizing the unique properties of colloidal quantum dots (NCs confined in three dimensions) in prototype solar cells and demonstrate that these unique systems have the potential to bypass the Shockley-Queisser single-junction limit for solar photon conversion. The solar cells are constructed using a low temperature solution based deposition of PbS or PbSe QDs as the absorber layer. A unique aspect of our devices is that the QDs exhibit multiple exciton generation with an efficiency that is ~ 2 to 3 times greater than the parental bulk semiconductor. I will discuss current status of MEG research and efforts toward further improve the MEG efficiency.