Increasing impact ionization rates in Si nanoparticles through surface engineering: A density functional study

Márton Vörös, Dario Rocca, Giulia Galli, Gergely T. Zimanyi, A. Gali

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

We propose design pathways to improve the efficiency of multiple exciton generation in nanoparticle-based solar cells by carrying out ab initio calculations of impact ionization (II) rates in semiconducting nanoparticles (NPs). In NPs with unreconstructed surfaces, quantum confinement has two competing effects: it enhances the effective Coulomb interaction and thus the II rates, but it also blue-shifts the gap, which tends to reduce the II rates. The competition of these effects determines the utility of NP-based solar cells. We report that surface reconstruction of NPs can tip the balance towards the enhancement of II by creating a substantial density of states at lower energies. Our results suggest that manipulating the surfaces of NPs, e.g., by engineering the ligands and embedding structures, may lead to an efficient multiexciton generation within the solar spectrum.

Original languageEnglish
Article number155402
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume87
Issue number15
DOIs
Publication statusPublished - Apr 4 2013

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Impact ionization
engineering
Nanoparticles
ionization
nanoparticles
Solar cells
solar cells
Quantum confinement
Surface reconstruction
solar spectra
Coulomb interactions
blue shift
Excitons
embedding
Ligands
excitons
ligands
augmentation

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Increasing impact ionization rates in Si nanoparticles through surface engineering : A density functional study. / Vörös, Márton; Rocca, Dario; Galli, Giulia; Zimanyi, Gergely T.; Gali, A.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 87, No. 15, 155402, 04.04.2013.

Research output: Contribution to journalArticle

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