Preferential gallium for zinc cation exchange in InZnP nanocrystals leads to photoluminescence enhancement
Nicholas Kirkwood a, Francesca Pietra a, Luca De Trizio b, Anne Hoekstra a, Lennart Kleibergen a, Rolf Koole c, Patrick Baesjou c, Nicolas Renaud a, Liberato Manna b, Arjan Houtepen a
a Chemical Engineering, Optoelectronic Materials, TU Delft, Julianalaan 136, 2628 BL Delft, The Netherlands, Netherlands
b CompuNet, Istituto Italiano di Tecnologia (IIT), Genova, Genova, Italy
c Philips Research Eindhoven, High Tech Campus 4, Eindhoven, 5656 AE, Netherlands
Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe September Meeting 2017 (NFM17)
SE1: Fundamental Processes in Semiconductor Nanocrystals
Barcelona, Spain, 2017 September 4th - 9th
Organizers: Arjan Houtepen and Zeger Hens
Poster, Nicholas Kirkwood, 151
Publication date: 20th June 2016

InP based nanocrystals (NCs) are a promising low-toxicity alternative to cadmium-based NCs for light emitting applications. However, achieving near-unity photoluminescent quantum yields (PL QYs) and high photostability has proved a challenge for InP NCs. Some progress has been made by adding Zn2+ salts to the synthesis of InP NCs, which we have shown results in the the formation of InZnP alloy nanocrystals and an improvement of their PL QY from < 1% (InP) up to 15% (InZnP) [1]. Further improvements in PL up to 50% have been reported by Kim et al. [2] by the addition of Ga3+ salts to InZnP NCs, which they attribute to the growth of a GaP shell via a cation exchange between Ga3+ and In3+.

In this presentation we will argue that the PL enhancement afforded by Ga3+ is actually the result of a preferential cation exchange between Ga3+ and Zn2+.[3] This is based on the combination of optical spectroscopy, compositional analysis (ICP-AES) and electron microscopy to characterise the reaction between Ga3+ and InZnP NCs as a function of added Ga3+. The results show a strong dependence on the zinc content in the starting nanocrystals, and suggest the gradual formation of a highly luminescent InZnP/InGaP graded core-shell structure via cation exchange. These results provide important mechanistic insights into recent improvements in InP-based QDs for luminescent applications.

[1] Pietra, F.; de Trizio, L. et al. ACS Nano 2016, 10, 4754–62.

[2] Kim, S.; Kim, T.; et al. Journal of the American Chemical Society 2012, 134, 3804–3809.

[3] Pietra, F; Kirkwood, N; de Trizio, L et al. Chemistry of Materials 2017 (10.1021/acs.chemmater.7b00848).

 

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