Numerical Study of Carrier Multiplication Pathways in Nanocrystalline and Bulk Form of PbSe

Employing the interband exciton scattering model, we have performed a numerical study of the direct photogeneration and population relaxation processes contributing to carrier multiplication (CM) in nanocrystalline and bulk PbSe. We argue that in both cases the impact ionization is the main mechanisms of CM. This explains weak contribution of the direct photogeneration to the total quantum efficiency (QE). Investigated size scaling of QE in NCs and comparison to the bulk limit provide microscopic insight in the experimentally observed trends.Comment: 4 pages, 3 figures (revised version) Accepted for publication in Physical Review Letter