Seven excitons at a cost of one

Redefining the limits for conversion efficiency of photons into charge carriers

Richard D. Schaller, Milan Sykora, Jeffrey M. Pietryga, Victor I. Klimov

Research output: Contribution to journalArticle

431 Citations (Scopus)

Abstract

The performance of photovoltaic and photochemical devices is directly linked to the efficiency with which absorbed photons are converted into electron hole pairs (excitons). A usual assumption is that one photon produces a single exciton, while the photon energy in the excess of the material's energy gap (the gap that separates the conduction from the valence band) is wasted as heat. Here we experimentally demonstrate that using semiconductor nanocrystals we can reduce this energy loss to a nearly absolute minimum allowed by energy conservation by producing multiple excitons per single photon. Specifically, we generate seven excitons from a photon with an energy of 7.8 energy gaps, which corresponds to only ∼10% energy loss, while in the normal scenario (one photon produces one exciton) ∼90% of the photon energy would be dissipated as heat. Such large yields of charge carriers (photon-to-exciton conversion efficiency up to 700%) has the potential to dramatically increase the performance of photovoltaic cells and can greatly advance solar fuel producing technologies.

Original languageEnglish
Pages (from-to)424-429
Number of pages6
JournalNano Letters
Volume6
Issue number3
DOIs
Publication statusPublished - Mar 2006

Fingerprint

Charge carriers
Excitons
Conversion efficiency
charge carriers
Photons
excitons
costs
photons
Costs
Energy dissipation
Energy gap
energy dissipation
heat
LDS 751
Photovoltaic cells
photovoltaic cells
energy conservation
Valence bands
Nanocrystals
energy

ASJC Scopus subject areas

  • Materials Science(all)
  • Electronic, Optical and Magnetic Materials
  • Chemistry (miscellaneous)

Cite this

Seven excitons at a cost of one : Redefining the limits for conversion efficiency of photons into charge carriers. / Schaller, Richard D.; Sykora, Milan; Pietryga, Jeffrey M.; Klimov, Victor I.

In: Nano Letters, Vol. 6, No. 3, 03.2006, p. 424-429.

Research output: Contribution to journalArticle

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