Colloidal Semiconductor Nanocrystals- Crystal Phase control to form - - PowerPoint PPT Presentation

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Colloidal Cu2ZnSn(SSe)4 (CZTSSe) Nanocrystals- Shape and Crystal Phase control to form Dots, Arrows, Ellipsoids and Rods

Shalini Singh, Pai Liu, Claudia Coughlan, Matteo Lusi, Kevin M. Ryan Materials and Surface Science Institute, University of Limerick, Limerick, Ireland.

Colloidal Semiconductor Nanocrystals- Structure as Resolved by TEM

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Semiconductor Metal Chalcogenide Nanocrystals

Zn In Cu Cu Zn Sn S S S Se

• Low Toxicity
• Earth Abundance
• Band Gap Tunability

I II III IV VI Element Groups

Singh A., Singh S., Levcenko S., Unold T., Laffir F. and Ryan K. M. Angew. Chem. Int. Ed. 2013, 52, 9120

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(002)

Colloidal Approach Nanocrystal Growth

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Challenges in the Synthesis of CZTSSe Nanocrystals

 Five elements  Multiple precursors  Reactivity differences of metal precursors  Narrow temperature window  Wide choice of ligands  Size distribution  Phase selection

Singh S. and Ryan K. M. J. Phy. Chem. Lett. 2015, 6, 3141

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Phase and Shape Controlled Synthesis of CZTSSe Nanocrystals

Zinc -Blende

Singh S., Liu P., Singh A., Coughlan C., Wang J., Lussi M. and Ryan K. M . Chem Mater. 2015, 27, 4742.

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Ligands: Oleylamine and phosphonic ligands Precursors: Copper chloride, zinc and tin acetates, thiol, diphenyldiselenide Temperature: 150-160 °C injection /250-270 °Cgrowth.

Ellipsoidal Shaped Polytypic CZTSSe Nanocrystals

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0.1 µm 0.1 µm

5 nm 5 nm

50 nm 50 nm 50 nm 50 nm

5 nm 5 nm

(1 min) (3 min) (5 min) (10 min)

5 nm

Time Dependent Aliquot Study of Ellipsoidal Nanocrystals

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Ligands: Oleylamine and phosphonic ligands Precursors: Metal acetates, thiol, diphenyldiselenide Temperature: 150-160 °C injection /250-270 °Cgrowth.

Arrow Shaped Polytypic CZTSSe Nanocrystals

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2 nm 2 nm 2 nm 2 nm

2 nm

(1 min) (3 min) (5 min) (10 min) (e)

WZ (001)

Time Dependent Aliquot Study of Arrow Shaped Nanocrystals

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Bullet Shaped Polytypic CZTSSe Nanocrystals

Two step process: 1. Wurtzite Nanocrystals synthesis- Copper acetylacetonate, zinc and tin acetates, thiol, DPDSe in OLA.

• 2. Post-treatment with TOPO-ODPA-Se.S in OLA at 270 °C.

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Formation Pathway for Bullet Shaped Nanocrystals

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Synthesis of Wurtzite CZTSSe Nanorods

Ligands: ODE, TOPO Precursors: Copper acetylacetonate, zinc and tin acetate, DDT, DPDSe. Temperature: 150-160 °C

injection /250-270 °Cgrowth.

Cu-2 mmol Cu-1.5 mmol Cu-1.2 mmol Cu-1.0 mmol Cu-0.8 mmol

Cu-0.8 mmol Cu-1.0 mmol Cu-1.2 mmol Cu-1.5 mmol Cu-2 mmol

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Conclusion

• A range of synthetic approaches were developed to obtain control over shape

and phase of anisotropic CZTSSe nanocrystals.

• The combination of coordinating solvent (OLA), TOPO and PAs entails the

evolution of atypical polytypic heterostructure whose shape could be controlled by the nature of metal precursors.

• The concomitant polytypism could be ruled out by replacing OLA and PAs by

non-coordinating solvent (ODE).

• Wurtzite nanorods are formed whose aspect ratio could be increased by

gradual reduction of Cu concentrations in the initial reaction flask.

• This study confirms the ability to controllably engineer the anisotropic shape

and phase of complex quinary nanostructures and gives better understanding of shape evolution in compound copper based semiconductor nanocrystals.

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Acknowledgment

Supervisor: Dr Kevin M. Ryan Dr Ajay Singh Dr Jianjun Wang Dr Yina Guo Nanoresearch Group