Electron transport phenomena at the interface of Al electrode and heavily doped degenerate ZnO nanoparticles in quantum dot light emitting diode

Yeon Ju Lee, Hong Hee Kim, Yun Jae Lee, Jung Hyuk Kim, Heon Jin Choi, Won Kook Choi

Research output: Contribution to journalArticle

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Abstract

ZnO nanoparticles (NPs) of 4-5 nm, widely adopted as an electron transport layer (ETL) in quantum dot light emitting diodes (QD-LEDs), were synthesized using the solution-precipitation process. It is notable that synthesized ZnO NPs are highly degenerate intrinsic semiconductors and their donor concentration can be increased up to N D = 6.9 ×1021 cm-3 by annealing at 140 °C in air. An optical bandgap increase of as large as 0.16-0.33 eV by degeneracy is explained well by the Burstein-Moss shift. In order to investigate the influence of intrinsic defects of ZnO NP ETLs on the performance of QD-LED devices without a combined annealing temperature between ZnO NP ETLs and the emissive QD layer, pre-annealed ZnO NPs at 60 °C, 90 °C, 140 °C, and 180 °C were spin-coated on the annealed QD layer without further post-annealing. As the annealing temperature increases from 60 °C to 180 °C, the defect density related to oxygen vacancy (V O) in ZnO NPs is reduced from 34.4% to 17.8%, whereas the defect density of interstitial Zn (Zni) is increased. Increased Zni reduces the width (W) of the depletion region from 0.21 to 0.12 nm and lowers the Schottky barrier (FB) between ZnO NPs and the Al electrode from 1.19 to 0.98 eV. We reveal for the first time that carrier conduction between ZnO NP ETLs and the Al electrode is largely affected by the concentration of Zni above the conduction band minimum, and effectively described by space charge limited current and trap charge limited current models.

Original languageEnglish
Article number035207
JournalNanotechnology
Volume30
Issue number3
DOIs
Publication statusPublished - 2019 Jan 18

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Semiconductor quantum dots
Light emitting diodes
Nanoparticles
Electrodes
Annealing
Defect density
Electron Transport
Optical band gaps
Oxygen vacancies
Conduction bands
Electric space charge
Semiconductor materials
Temperature
Defects
Air

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering
  • Electrical and Electronic Engineering

Cite this

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title = "Electron transport phenomena at the interface of Al electrode and heavily doped degenerate ZnO nanoparticles in quantum dot light emitting diode",
abstract = "ZnO nanoparticles (NPs) of 4-5 nm, widely adopted as an electron transport layer (ETL) in quantum dot light emitting diodes (QD-LEDs), were synthesized using the solution-precipitation process. It is notable that synthesized ZnO NPs are highly degenerate intrinsic semiconductors and their donor concentration can be increased up to N D = 6.9 ×1021 cm-3 by annealing at 140 °C in air. An optical bandgap increase of as large as 0.16-0.33 eV by degeneracy is explained well by the Burstein-Moss shift. In order to investigate the influence of intrinsic defects of ZnO NP ETLs on the performance of QD-LED devices without a combined annealing temperature between ZnO NP ETLs and the emissive QD layer, pre-annealed ZnO NPs at 60 °C, 90 °C, 140 °C, and 180 °C were spin-coated on the annealed QD layer without further post-annealing. As the annealing temperature increases from 60 °C to 180 °C, the defect density related to oxygen vacancy (V O) in ZnO NPs is reduced from 34.4{\%} to 17.8{\%}, whereas the defect density of interstitial Zn (Zni) is increased. Increased Zni reduces the width (W) of the depletion region from 0.21 to 0.12 nm and lowers the Schottky barrier (FB) between ZnO NPs and the Al electrode from 1.19 to 0.98 eV. We reveal for the first time that carrier conduction between ZnO NP ETLs and the Al electrode is largely affected by the concentration of Zni above the conduction band minimum, and effectively described by space charge limited current and trap charge limited current models.",
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Electron transport phenomena at the interface of Al electrode and heavily doped degenerate ZnO nanoparticles in quantum dot light emitting diode. / Lee, Yeon Ju; Kim, Hong Hee; Lee, Yun Jae; Kim, Jung Hyuk; Choi, Heon Jin; Choi, Won Kook.

In: Nanotechnology, Vol. 30, No. 3, 035207, 18.01.2019.

Research output: Contribution to journalArticle

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T1 - Electron transport phenomena at the interface of Al electrode and heavily doped degenerate ZnO nanoparticles in quantum dot light emitting diode

AU - Lee, Yeon Ju

AU - Kim, Hong Hee

AU - Lee, Yun Jae

AU - Kim, Jung Hyuk

AU - Choi, Heon Jin

AU - Choi, Won Kook

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Y1 - 2019/1/18

N2 - ZnO nanoparticles (NPs) of 4-5 nm, widely adopted as an electron transport layer (ETL) in quantum dot light emitting diodes (QD-LEDs), were synthesized using the solution-precipitation process. It is notable that synthesized ZnO NPs are highly degenerate intrinsic semiconductors and their donor concentration can be increased up to N D = 6.9 ×1021 cm-3 by annealing at 140 °C in air. An optical bandgap increase of as large as 0.16-0.33 eV by degeneracy is explained well by the Burstein-Moss shift. In order to investigate the influence of intrinsic defects of ZnO NP ETLs on the performance of QD-LED devices without a combined annealing temperature between ZnO NP ETLs and the emissive QD layer, pre-annealed ZnO NPs at 60 °C, 90 °C, 140 °C, and 180 °C were spin-coated on the annealed QD layer without further post-annealing. As the annealing temperature increases from 60 °C to 180 °C, the defect density related to oxygen vacancy (V O) in ZnO NPs is reduced from 34.4% to 17.8%, whereas the defect density of interstitial Zn (Zni) is increased. Increased Zni reduces the width (W) of the depletion region from 0.21 to 0.12 nm and lowers the Schottky barrier (FB) between ZnO NPs and the Al electrode from 1.19 to 0.98 eV. We reveal for the first time that carrier conduction between ZnO NP ETLs and the Al electrode is largely affected by the concentration of Zni above the conduction band minimum, and effectively described by space charge limited current and trap charge limited current models.

AB - ZnO nanoparticles (NPs) of 4-5 nm, widely adopted as an electron transport layer (ETL) in quantum dot light emitting diodes (QD-LEDs), were synthesized using the solution-precipitation process. It is notable that synthesized ZnO NPs are highly degenerate intrinsic semiconductors and their donor concentration can be increased up to N D = 6.9 ×1021 cm-3 by annealing at 140 °C in air. An optical bandgap increase of as large as 0.16-0.33 eV by degeneracy is explained well by the Burstein-Moss shift. In order to investigate the influence of intrinsic defects of ZnO NP ETLs on the performance of QD-LED devices without a combined annealing temperature between ZnO NP ETLs and the emissive QD layer, pre-annealed ZnO NPs at 60 °C, 90 °C, 140 °C, and 180 °C were spin-coated on the annealed QD layer without further post-annealing. As the annealing temperature increases from 60 °C to 180 °C, the defect density related to oxygen vacancy (V O) in ZnO NPs is reduced from 34.4% to 17.8%, whereas the defect density of interstitial Zn (Zni) is increased. Increased Zni reduces the width (W) of the depletion region from 0.21 to 0.12 nm and lowers the Schottky barrier (FB) between ZnO NPs and the Al electrode from 1.19 to 0.98 eV. We reveal for the first time that carrier conduction between ZnO NP ETLs and the Al electrode is largely affected by the concentration of Zni above the conduction band minimum, and effectively described by space charge limited current and trap charge limited current models.

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