A statistical understanding of multiple exciton generation in PbSe semiconductor nanostructures

We propose a simple statistical model, based on Fermi statistical theory and impact ionization mechanism, to resolve the controversies over the effects of multiple exciton generation (MEG) in PbSe quantum dots (QDs). We have confirmed that MEG indeed occurs in PbSe QDs. Also, we have found out that there exists a critical radius RcRc (∼9 nm) such that the MEG efficiency of PbSe QDs is smaller than that of the bulk counterpart if RRcR>Rc. Moreover, we have found out that the MEG threshold energy calculated for PbSe QDs shows a universal behavior. The present work provides a powerful theoretical means not only for further experimental investigations into the MEG effects in semiconductor nanostructures, but for their applications in photovoltaic devices.

► We propose a statistical model to resolve the controversies over the MEG effects. ► We confirm the MEG in PbSe quantum dots. ► We examine the MEG efficiency of PbSe quantum dots and the bulk counterpart. ► We find out the MEG threshold energy.