Ultrafast dynamics of multiple exciton harvesting in the CdSe-ZnO system: Electron injection versus auger recombination

Karel Žídek, Kaibo Zheng, Mohamed Abdellah, Nils Lenngren, Pavel Chábera, Tõnu Pullerits

Research output: Contribution to journalArticlepeer-review

78 Citations (Scopus)

Abstract

We study multiple electron transfer from a CdSe quantum dot (QD) to ZnO, which is a prerequisite for successful utilization of multiple exciton generation for photovoltaics. By using ultrafast time-resolved spectroscopy we observe competition between electron injection into ZnO and quenching of multiexcitons via Auger recombination. We show that fast electron injection dominates over biexcitonic Auger recombination and multiple electrons can be transferred into ZnO. A kinetic component with time constant of a few tens of picoseconds was identified as the competition between injection of the second electron from a doubly excited QD and a trion Auger recombination. Moreover, we demonstrate that the multiexciton harvesting efficiency changes significantly with QD size. Within a narrow QD diameter range from 2 to 4 nm, the efficiency of electron injection from a doubly excited QD can vary from 30% to 70% in our system.

Original languageEnglish
Pages (from-to)6393-6399
Number of pages7
JournalNano Letters
Volume12
Issue number12
DOIs
Publication statusPublished - Dec 12 2012
Externally publishedYes

Keywords

  • electron transport
  • multiple exciton generation
  • Quantum dots
  • solar cell
  • ultrafast transient absorption

ASJC Scopus subject areas

  • Bioengineering
  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics
  • Mechanical Engineering

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