High efficiency and optical anisotropy in double-heterojunction nanorod light-emitting diodes

Sooji Nam, Nuri Oh, You Zhai, Moonsub Shim

Research output: Contribution to journalArticlepeer-review

Abstract

Recent advances in colloidal quantum dot light-emitting diodes (QD-LEDs) have led to efficiencies and brightness that rival the best organic LEDs. Nearly ideal internal quantum efficiency being achieved leaves light outcoupling as the only remaining means to improve external quantum efficiency (EQE) but that might require radically different device design and reoptimization. However, the current state-of-the-art QD-LEDs are based on spherical core/shell QDs, and the effects of shape and optical anisotropy remain essentially unexplored. Here, we demonstrate solution-processed, red-emitting double-heterojunction nanorod (DHNR)-LEDs with efficient hole transport exhibiting low threshold voltage and high brightness (76»000 cd m-2) and efficiencies (EQE = 12%, current efficiency = 27.5 cd A-1, and power efficiency = 34.6 lm W-1). EQE exceeding the expected upper limit of ∼8% (based on ∼20% light outcoupling and solution photoluminescence quantum yield of ∼40%) suggests shape anisotropy and directional band offsets designed into DHNRs play an important role in enhancing light outcoupling.

Original languageEnglish (US)
Pages (from-to)878-885
Number of pages8
JournalACS Nano
Volume9
Issue number1
DOIs
StatePublished - Jan 27 2015

Keywords

  • double-heterojunction nanorods
  • high efficiencies
  • light outcoupling
  • light-emitting diodes
  • optical anisotropy

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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