Exciton extraction in nanocrystal solar cells

• The efficiency of exciton extraction from nanocrystals is studied through a phenomenological model.
• The incident photons generate e–h pairs within individual nanocrystals.
• The photocurrent generated by the nanocrystals (NC׳s) are defined as the fraction of e–h pairs escaping from the NCÕs through the shell layer.
• Depending on the parameters the conversion efficiency can be up to 118%.

The efficiency of exciton extraction from nanocrystals is defined as the ratio of the number of extracted excitons to the number of absorbed photons. This efficiency is studied here based on a phenomenological model parameterized by recent experimental results in CdSe nanocrystals. Several possibilities of interplay among all possible electronic transition rates (Auger recombination, impact ionization, radiative recombination and electron–hole escape) are explored showing the possibility of obtaining efficiencies above 100% when multiple exciton generation processes are taken into account.