Quantum Dot Light-Emitting Diode with Ligand-Exchanged ZnCuInS<SUB>2</SUB> Quantum Dot

Takeshi FUKUDA; Masatomo HISHINUMA; Junya MAKI; Hironao SASAKI

doi:10.1587/transele.E100.C.943

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Quantum Dot Light-Emitting Diode with Ligand-Exchanged ZnCuInS₂ Quantum Dot

Takeshi FUKUDA, Masatomo HISHINUMA, Junya MAKI, Hironao SASAKI

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Nowadays, semiconductor quantum dots have attracted intense attention as emissive materials for light-emitting diodes, due to their high photoluminescence quantum yield and the controllability of their photoluminescence spectrum by changing the core diameter. In general, semiconductor quantum dots contain large amounts of organic ligands around the core/shell structure to obtain dispersibility in solution, which leads to solution processability of the semiconductor quantum dot. Furthermore, organic ligands, such as straight alkyl chains, are generally insulating materials, which affects the carrier transport in thin-film light-emitting diodes. However, a detailed investigation has not been performed yet. In this paper, we investigated the luminance characteristics of quantum-dot light-emitting diodes containing ZnCuInS₂ quantum dots with different carbon chain lengths of alkyl thiol ligands as emitting layers. By evaluating the CH₂/CH₃ ratio from Fourier-transform infrared spectra and thermal analysis, it was found that approximately half of the oleylamine ligands were converted to alkyl thiol ligands, and the evaporation temperature increased with increasing carbon chain length of the alkyl thiol ligands based on thermogravimetric analysis. However, the photoluminescence quantum yield and the spectral shape were almost the same, even after the ligand-exchange process from the oleylamine ligand to the alkyl thiol ligand. The peak wavelength of the photoluminescence spectra and the photoluminescence quantum yield were approximately 610 nm and 10%, respectively, for all samples. In addition, the surface morphology of spin coated ZnCuInS₂ quantum-dot layers did not change after the ligand-exchange process, and the root-mean-square roughness was around 1 nm. Finally, the luminance efficiency of an inverted device structure increased with decreasing carbon chain length of the alkyl thiol ligands, which were connected around the ZnCuInS₂ quantum dots. The maximum luminance and current efficiency were 86 cd/m² and 0.083 cd/A, respectively.

Publication: IEICE TRANSACTIONS on Electronics Vol.E100-C No.11 pp.943-948

Publication Date: 2017/11/01

Publicized

Online ISSN: 1745-1353

DOI: 10.1587/transele.E100.C.943

Type of Manuscript: Special Section INVITED PAPER (Special Section on Electronic Displays)

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Authors

Takeshi FUKUDA
  Saitama University
Masatomo HISHINUMA
  Saitama University
Junya MAKI
  Saitama University
Hironao SASAKI
  Saitama University

Keyword

semiconductor quantum dot, quantum dot light-emitting diode, ligand exchange, alkyl thiol

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Takeshi FUKUDA, Masatomo HISHINUMA, Junya MAKI, Hironao SASAKI, "Quantum Dot Light-Emitting Diode with Ligand-Exchanged ZnCuInS2 Quantum Dot" in IEICE TRANSACTIONS on Electronics, vol. E100-C, no. 11, pp. 943-948, November 2017, doi: 10.1587/transele.E100.C.943.
Abstract: Nowadays, semiconductor quantum dots have attracted intense attention as emissive materials for light-emitting diodes, due to their high photoluminescence quantum yield and the controllability of their photoluminescence spectrum by changing the core diameter. In general, semiconductor quantum dots contain large amounts of organic ligands around the core/shell structure to obtain dispersibility in solution, which leads to solution processability of the semiconductor quantum dot. Furthermore, organic ligands, such as straight alkyl chains, are generally insulating materials, which affects the carrier transport in thin-film light-emitting diodes. However, a detailed investigation has not been performed yet. In this paper, we investigated the luminance characteristics of quantum-dot light-emitting diodes containing ZnCuInS₂ quantum dots with different carbon chain lengths of alkyl thiol ligands as emitting layers. By evaluating the CH₂/CH₃ ratio from Fourier-transform infrared spectra and thermal analysis, it was found that approximately half of the oleylamine ligands were converted to alkyl thiol ligands, and the evaporation temperature increased with increasing carbon chain length of the alkyl thiol ligands based on thermogravimetric analysis. However, the photoluminescence quantum yield and the spectral shape were almost the same, even after the ligand-exchange process from the oleylamine ligand to the alkyl thiol ligand. The peak wavelength of the photoluminescence spectra and the photoluminescence quantum yield were approximately 610 nm and 10%, respectively, for all samples. In addition, the surface morphology of spin coated ZnCuInS₂ quantum-dot layers did not change after the ligand-exchange process, and the root-mean-square roughness was around 1 nm. Finally, the luminance efficiency of an inverted device structure increased with decreasing carbon chain length of the alkyl thiol ligands, which were connected around the ZnCuInS₂ quantum dots. The maximum luminance and current efficiency were 86 cd/m² and 0.083 cd/A, respectively.
URL: https://global.ieice.org/en_transactions/electronics/10.1587/transele.E100.C.943/_p

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@ARTICLE{e100-c_11_943,
author={Takeshi FUKUDA, Masatomo HISHINUMA, Junya MAKI, Hironao SASAKI, },
journal={IEICE TRANSACTIONS on Electronics},
title={Quantum Dot Light-Emitting Diode with Ligand-Exchanged ZnCuInS2 Quantum Dot},
year={2017},
volume={E100-C},
number={11},
pages={943-948},
abstract={Nowadays, semiconductor quantum dots have attracted intense attention as emissive materials for light-emitting diodes, due to their high photoluminescence quantum yield and the controllability of their photoluminescence spectrum by changing the core diameter. In general, semiconductor quantum dots contain large amounts of organic ligands around the core/shell structure to obtain dispersibility in solution, which leads to solution processability of the semiconductor quantum dot. Furthermore, organic ligands, such as straight alkyl chains, are generally insulating materials, which affects the carrier transport in thin-film light-emitting diodes. However, a detailed investigation has not been performed yet. In this paper, we investigated the luminance characteristics of quantum-dot light-emitting diodes containing ZnCuInS₂ quantum dots with different carbon chain lengths of alkyl thiol ligands as emitting layers. By evaluating the CH₂/CH₃ ratio from Fourier-transform infrared spectra and thermal analysis, it was found that approximately half of the oleylamine ligands were converted to alkyl thiol ligands, and the evaporation temperature increased with increasing carbon chain length of the alkyl thiol ligands based on thermogravimetric analysis. However, the photoluminescence quantum yield and the spectral shape were almost the same, even after the ligand-exchange process from the oleylamine ligand to the alkyl thiol ligand. The peak wavelength of the photoluminescence spectra and the photoluminescence quantum yield were approximately 610 nm and 10%, respectively, for all samples. In addition, the surface morphology of spin coated ZnCuInS₂ quantum-dot layers did not change after the ligand-exchange process, and the root-mean-square roughness was around 1 nm. Finally, the luminance efficiency of an inverted device structure increased with decreasing carbon chain length of the alkyl thiol ligands, which were connected around the ZnCuInS₂ quantum dots. The maximum luminance and current efficiency were 86 cd/m² and 0.083 cd/A, respectively.},
keywords={},
doi={10.1587/transele.E100.C.943},
ISSN={1745-1353},
month={November},}

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TY - JOUR
TI - Quantum Dot Light-Emitting Diode with Ligand-Exchanged ZnCuInS2 Quantum Dot
T2 - IEICE TRANSACTIONS on Electronics
SP - 943
EP - 948
AU - Takeshi FUKUDA
AU - Masatomo HISHINUMA
AU - Junya MAKI
AU - Hironao SASAKI
PY - 2017
DO - 10.1587/transele.E100.C.943
JO - IEICE TRANSACTIONS on Electronics
SN - 1745-1353
VL - E100-C
IS - 11
JA - IEICE TRANSACTIONS on Electronics
Y1 - November 2017
AB - Nowadays, semiconductor quantum dots have attracted intense attention as emissive materials for light-emitting diodes, due to their high photoluminescence quantum yield and the controllability of their photoluminescence spectrum by changing the core diameter. In general, semiconductor quantum dots contain large amounts of organic ligands around the core/shell structure to obtain dispersibility in solution, which leads to solution processability of the semiconductor quantum dot. Furthermore, organic ligands, such as straight alkyl chains, are generally insulating materials, which affects the carrier transport in thin-film light-emitting diodes. However, a detailed investigation has not been performed yet. In this paper, we investigated the luminance characteristics of quantum-dot light-emitting diodes containing ZnCuInS₂ quantum dots with different carbon chain lengths of alkyl thiol ligands as emitting layers. By evaluating the CH₂/CH₃ ratio from Fourier-transform infrared spectra and thermal analysis, it was found that approximately half of the oleylamine ligands were converted to alkyl thiol ligands, and the evaporation temperature increased with increasing carbon chain length of the alkyl thiol ligands based on thermogravimetric analysis. However, the photoluminescence quantum yield and the spectral shape were almost the same, even after the ligand-exchange process from the oleylamine ligand to the alkyl thiol ligand. The peak wavelength of the photoluminescence spectra and the photoluminescence quantum yield were approximately 610 nm and 10%, respectively, for all samples. In addition, the surface morphology of spin coated ZnCuInS₂ quantum-dot layers did not change after the ligand-exchange process, and the root-mean-square roughness was around 1 nm. Finally, the luminance efficiency of an inverted device structure increased with decreasing carbon chain length of the alkyl thiol ligands, which were connected around the ZnCuInS₂ quantum dots. The maximum luminance and current efficiency were 86 cd/m² and 0.083 cd/A, respectively.
ER -