Efficient White-Light-Emitting Diodes Fabricated from Highly Fluorescent Copper Indium Sulfide Core/Shell Quantum Dots
- Authors
- Song, Woo-Seuk; Yang, Heesun
- Issue Date
- 22-May-2012
- Publisher
- AMER CHEMICAL SOC
- Keywords
- copper indium sulfide; quantum dots; Cu/In molar ratio; white LED
- Citation
- CHEMISTRY OF MATERIALS, v.24, no.10, pp.1961 - 1967
- Journal Title
- CHEMISTRY OF MATERIALS
- Volume
- 24
- Number
- 10
- Start Page
- 1961
- End Page
- 1967
- URI
- https://scholarworks.bwise.kr/hongik/handle/2020.sw.hongik/18956
- DOI
- 10.1021/cm300837z
- ISSN
- 0897-4756
- Abstract
- Copper indium sulfide (CIS) quantum dots (QDs) with different Cu/In molar ratios of 1/1, 1/2, and 1/4 are synthesized via a hot colloidal route. The band gap energy of CIS QDs is observed to be dependent on Cu/In ratio, exhibiting a higher band gap from more Cu-deficient QDs. The emission wavelengths of all CIS QDs belong to a deep red region (665-717 nm) with relatively low quantum yields (Qys) of 8.6-12.7%. Compared to respective original core QDs, the absorption peaks of all CIS/ZnS QDs are blue-shifted, and their emission wavelengths move to a higher energy accordingly, showing a quite tunable emission from yellow to red. The effective surface passivation by a ZnS overlayer results in a dramatic increase in QY of CIS/ZnS QDs in the range of 68-78%. All CIS/ZnS QDs are tested as wavelength converters for the fabrication of QD-based light-emitting diodes (LEDs). QD-based white LEDs that consist of only a single type of QD are for the first time realized by applying yellow-emitting CIS/ZnS QDs as a result of the appropriate color mixing between blue emission from a LED chip and yellow emission from QDs. Detailed electroluminescent properties including color rendering index, Commission Internationale de l'Eclairage (CIE) color. coordinates, and luminous efficiency of QD-based white LEDs are evaluated as a function of forward current.
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