Innovative Colloidal Nanostructures: Nanoplatelets and III-V quantum Dots

Innovative Colloidal Nanostructures: Nanoplatelets and III-V Quantum Dots

Colloidal Quantum Dots (QDs) are semiconductor nanocrystals in the 1 to 10 nm size range synthesized by wet chemistry process. Because of these small sizes, QDs are subject to quantum mechanical effects. One of the most remarkable one is the quantum confinement of the charge carriers. This effect leads to discrete transitions, much like in an atom or a molecule, with energies higher than the bulk and that are strongly dependent of the QDs sizes. These unique properties have allowed QDs to emerge as a novel class of opto-electronic materials over the last 25 years. The most advanced application of colloidal QDs, at least from a research valorization perspective, is their commercial use in liquid crystal displays (LCDs). First launched in 2013, sales of QDs-enhanced LCDs are expected to achieve 18 million units in 2018.

Significant advances have been made in the synthesis of QDs since the beginning of the 1990s. The shape of the nanoparticles can now be finely controlled, and nanoparticles with various shapes have been synthesized. In particular, colloidal nanoplatelets are atomically flat nanostructures that present only one dimension of quantum confinement.¹ In this lecture, I first present how the nanoplatelets dimensions can be perfectly controlled via inventive synthesis protocols and what this implies on the nanoplatelets optical properties.^2–4

To facilitate the use of nanocrystals in the industry, interest is shifting from the well-characterized cadmium-based QDs to cadmium-free alternatives such as indium phosphide. We recently proposed protocols based on aminophosphine-type precursors that allow for a cost efficient, up-scaled syntheses of indium phosphide (InP) QDs of different sizes.⁵ A detailed understanding of the reaction chemistry is a key in the development of colloidal QDs synthesis. I present a complete investigation of chemical reactions leading to the formation of InP starting from aminophosphine-type precursors.⁶ This mechanism is innovative in the sense that it points out a double role of the phosphorus precursor in the reaction as both a reducing agent and the source of the phosphorus needed to form InP. Its understanding furthers the general use of aminopnictogens for the synthesis of III-V QDs.⁷ Finally, I show that InP QDs can be processed in polymer layer and that their structure can be optimized in order to obtain more efficient and cheaper lighting devices.⁸

References

(1) Ithurria, S.; Tessier, M. D.; Mahler, B.; Lobo, R. P. S. M.; Dubertret, B.; Efros, A. L. Nat. Mater. 2011, 10, 936–941.

(2) Tessier, M. D.; Mahler, B.; Nadal, B.; Heuclin, H.; Pedetti, S.; Dubertret, B. Nano Lett. 2013, 13, 3321–3328.

(3) Tessier, M. D.; Spinicelli, P.; Dupont, D.; Patriarche, G.; Ithurria, S.; Dubertret, B. Nano Lett. 2014, 14, 207–213.

(4) Tessier, M. D.; Javaux, C.; Maksimovic, I.; Loriette, V.; Dubertret, B. ACS Nano 2012, 6, 6751–6758.

(5) Tessier, M. D.; Dupont, D.; De Nolf, K.; De Roo, J.; Hens, Z. Chem. Mater. 2015, 27, 4893–4898.

(6) Tessier, M. D.; De Nolf, K.; Dupont, D.; Sinnaeve, D.; De Roo, J.; Hens, Z. J. Am. Chem. Soc. 2016, 138, 5923–5929.

(7) Grigel, V.; Dupont, D.; De Nolf, K.; Hens, Z.; Tessier, M. D. J. Am. Chem. Soc. 2016, 138, 13485–13488.

(8) Dupont, D.; Tessier, M. D.; Smet, P. F.; Hens, Z. Adv. Mater. 2017. DOI: 10.1002/adma.201700686