Proceedings of nanoGe September Meeting 2017 (NFM17)
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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