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Homogeneously Alloyed CdSe1-xSx Quantum Dots (0 ≤ x ≤ 1)
Tangi Aubert, Marco Cirillo, Stijn Flamee, Rik Van Deun, Holger Lange,
Christian Thomsen, Zeger Hens
E-MRS Spring Meeting 2013, Strasbourg, France
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Tuning optical properties of QDs
size dependent
compositiondependent
alloyed QDs
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Alloyed QDs
Bailey et al., J. Am. Chem. Soc. 2003, 125, 7100; Swafford et al. J. Am. Chem. Soc. 2006, 128, 12299; Gurusinghe et al. J. Phys. Chem. C 2008, 112, 12795; Zheng et al. Adv. Mater. 2007, 19, 1475.
II-VI alloys: Cd(Se,Te), Cd(Se,S), Cd(Te,S), (Cd,Zn)Se, …
gradient homogeneouscore-shell
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Heterogeneous Se-ODE synthesis
S. Flamee, M. Cirillo, S. Abe, K. De Nolf, R. Gomes, T. Aubert, Z. Hens, submitted.S. Flamee, R. Dierick, M. Cirillo, D. Van Genechten, T. Aubert, Z. Hens, Dalton Trans. 2013. doi10.1039/c3dt50757bS. Flamee, Z. Hens, patent n°PCT/EP2012/072428, 2012.
Synthesis of CdSe, ZnSe, CuInSe2 and Cu2(Zn,Sn)Se4 QDs
heterogeneousSe-ODE
TC
ODE carboxylic acid
CdO
- open air (no flushing)- T = 260°C- 5 min reaction- nearly full yield- high solid load
allow large production
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Heterogeneous Se-ODE synthesis
T. Aubert, M. Cirillo, S. Flamee, R. Van Deun, H. Lange, C. Thomsen, Z. Hens, Chem. Mater., 10.1021/cm401019t
Heterogeneous Se-ODE vs. Homogeneous S-ODE
heterogeneousSe-ODE
homogeneousS-ODE
OR
equivalent reactivities towards CdCdSe CdS
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CdSe1-xSx synthesis
Tunable synthesis through entire composition range (0 ≤ x ≤ 1)
heterogeneousSe-ODE
homogeneousS-ODE
AND
1-x x
CdSe1-xSx
T. Aubert, M. Cirillo, S. Flamee, R. Van Deun, H. Lange, C. Thomsen, Z. Hens, Chem. Mater., 10.1021/cm401019t
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CdSe1-xSx alloyed QDs
Morphology and structure (TEM)
size can still be tuned with acid length
CdSe0.5S0.5
size = 3 nm (myristic acid)
T. Aubert, M. Cirillo, S. Flamee, R. Van Deun, H. Lange, C. Thomsen, Z. Hens, Chem. Mater., 10.1021/cm401019t
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CdSe1-xSx alloyed QDs
Morphology and structure (XRD)
lattice parameter follows Vegard’s law
T. Aubert, M. Cirillo, S. Flamee, R. Van Deun, H. Lange, C. Thomsen, Z. Hens, Chem. Mater., 10.1021/cm401019t
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CdSe1-xSx alloyed QDsMorphology and structure (Raman)
- LO shifts with composition- narrow FWHM for x = 0, 0.5 and 1- large FWHM for uneven compositions
fitted LO bands LO frequency and FWHM
homogeneous alloying
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CdSe1-xSx alloyed QDsOptical properties
absorption emission
T. Aubert, M. Cirillo, S. Flamee, R. Van Deun, H. Lange, C. Thomsen, Z. Hens, Chem. Mater., 10.1021/cm401019t
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CdSe1-xSx/CdS core-shell QDs
Li et al., J. Am. Chem. Soc. 2003, 125, 12567.
Synthesis: layer-by-layer (SILAR)
→ PL enhancement decreases with increasing S content in the core
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CdSe1-xSx/CdS core-shell QDs
Confinement energy:
Econf (CdSe1-xSx/CdS) = Eg (CdSe1-xSx/CdS) - Eg,∞ (CdSe1-xSx)
Eg,∞ (CdSe1-xSx) = (1-x)Eg (CdSe) + xEg (CdS) - bx(1-x)
T. Aubert, M. Cirillo, S. Flamee, R. Van Deun, H. Lange, C. Thomsen, Z. Hens, Chem. Mater., 10.1021/cm401019t
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Conclusion
CdSe1-xSx alloyed QDs
- fast, high yield and tunable synthesis
- homogeneous alloying (Raman spectroscopy)
- efficient tuning of the band gap
just accepted in Chemistry of Materials, DOI: 10.1021/cm401019t
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Aknowledgement
Thanks for your attention !
Max Kade Foundation