Multiple exciton generation in silicon quantum dot arrays: density functional perturbation theory computation

Abstract

We use the density functional theory (DFT) combined with the many-body perturbation theory to derive expressions for the rates of the optical photon→exciton and photon→bi-exciton processes in nanoparticles, and for quantum efficiency, all to the leading order in the screened Coulomb interaction between Kohn–Sham quasiparticles. Also, we calculate exciton→bi-exciton rates due to the impact ionisation (II) mechanism in Si₂₉H₃₆ quantum dots (QDs) with both crystalline and amorphous core structures, and in quasi-one dimensional (1-D) arrays constructed from these QDs. We observe significant dependence of the carrier multiplication rates on the structure’s morphology and structural disorder. Amorphous silicon QD arrays are predicted to have more efficient bi-exciton generation rates as a function of exciton energy compared to their crystalline counterparts, and the isolated QDs of both kinds.

Keywords:

• density functional theory
• quantum dots
• multiple exciton generation

Acknowledgements

A. Kryjevski acknowledges the use of computational resources of the Center for Computationally Assisted Science and Technology (CCAST) at North Dakota State University. D. Kilin acknowledges DOE, BES-Chemical Sciences and NERSC No. DEAC02- 05CH11231, allocation Award 86185 ‘Computational Modeling of Photo-catalysis and Photo-induced Charge Transfer Dynamics on Surfaces’ for providing computational resources.

Additional information

Funding

A. Kryjevski acknowledges financial support from the US Department of Energy [DE-FG52-08NA28921. D. Kilin acknowledges the South Dakota Governor’s Office of Economic Development and NSF award [EPS0903804] for financial support.