Charge Trapping in Bright and Dark States of Coupled PbS Quantum Dot Films

Jianbo Gao, Justin C. Johnson

Research output: Contribution to journalArticlepeer-review

85 Scopus Citations

Abstract

Analysis of photoluminescence (PL) from chemically treated lead sulfide (PbS) quantum dot (QD) films versus temperature reveals the effects of QD size and ligand binding on the motion of carriers between bright and dark trap states. For strongly coupled QDs, the PL exhibits temperature-dependent quenching and shifting consistent with charges residing in a shallow exponential tail of quasi-localized states below the band gap. The depth of the tail varies from 15 to 40 meV, similar to or smaller than exponential band tail widths measured for polycrystalline Si. The trap state distribution can be manipulated with QD size and surface treatment, and its characterization should provide a clearer picture of charge separation and percolation in disordered QD films than what currently exists.

Original languageAmerican English
Pages (from-to)3292-3303
Number of pages12
JournalACS Nano
Volume6
Issue number4
DOIs
StatePublished - 2012

NREL Publication Number

  • NREL/JA-5900-54629

Keywords

  • band tail
  • exiton
  • nanocrystal
  • photoluminescence
  • temperature
  • transport

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