Enhanced Luminance of CdSe/ZnS Quantum Dots Light-Emitting Diodes Using ZnO-Oleic Acid/ZnO Quantum Dots Double Electron Transport Layer

Da Young Lee, Hong Hee Kim, Ji Hyun Noh, Keun Yong Lim, Donghee Park, In Hwan Lee, Won Kook Choi

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

The widely used ZnO quantum dots (QDs) as an electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs) have one drawback. That the balancing of electrons and holes has not been effectively exploited due to the low hole blocking potential difference between the valence band (VB) (6.38 eV) of ZnO ETL and (6.3 eV) of CdSe/ZnS QDs. In this study, ZnO QDs chemically reacted with capping ligands of oleic acid (OA) to decrease the work function of 3.15 eV for ZnO QDs to 2.72~3.08 eV for the ZnO-OA QDs due to the charge transfer from ZnO to OA ligands and improve the efficiency for hole blocking as the VB was increased up to 7.22~7.23 eV. Compared to the QLEDs with a single ZnO QDs ETL, the ZnO-OA/ZnO QDs double ETLs optimize the energy level alignment between ZnO QDs and CdSe/ZnS QDs but also make the surface roughness of ZnO QDs smoother. The optimized glass/ITO/PEDOT:PSS/PVK//CdSe/ZnS//ZnO-OA/ZnO/Ag QLEDs enhances the maximum luminance by 5~9% and current efficiency by 16~35% over the QLEDs with a single ZnO QDs ETL, which can be explained in terms of trap-charge limited current (TCLC) and the Fowler-Nordheim (F-N) tunneling conduction mechanism.

Original languageEnglish
Article number2038
JournalNanomaterials
Volume12
Issue number12
DOIs
Publication statusPublished - 2022 Jun 1

Bibliographical note

Funding Information:
Acknowledgments: W.K. Choi and D. Park thank both the Materials, Components & Equipment Research Program funded by Gyeonggi Province (AICT11T2) and the KIST Institutional program. H.H. Kim acknowledges a partial support from the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (Grant No. 2021R1A66A3A01087644).

Funding Information:
Funding: This research was funded by both the Materials, Components & Equipment Research Program funded by Gyeonggi Province (AICT11T2) and the KIST Institutional program. This work is also partially supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (Grant No. 2021R1A66A3A01087644).

Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Keywords

  • QLEDs
  • ZnO-OA QDs
  • double ETL
  • electron transport layer
  • hole blocking

ASJC Scopus subject areas

  • General Chemical Engineering
  • General Materials Science

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