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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

tangi.aubert@ugent.be

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Aknowledgement

Thanks for your attention !

Max Kade Foundation