The synthesis of colloidal semiconductor nanocrystals is typically performed via hot-injection routes that suffer from a somewhat limited control over the growth kinetics. This leads to a broad distribution of nanoparticle sizes and poorly defined surface stoichiometries. To address this issue, we have developed an alternative growth strategy that relies on the stepwise, controllable evolution of nanocrystals sizes. As a result, fabricated nanocrystals exhibit well-defined surface morphologies and a small dispersion of particle diameters. By using different metal chalcogenide nanoparticles as a starting material, we are able to fabricate large quantum dots and core/shell nanocomposites utilizing a sequential deposition of fully-saturated cation and anion half-monolayers onto starting “seeds”. The layer-by-layer technique also allows us to deposit a shell material with a precise thickness on each nanoparticle in solution. Besides an expected benefit of the demonstrated synthetic strategy to QD-LED applications, where narrow emission lines are important, the sequential ionic synthesis is expected to be useful in applications employing nanocrystal solids (photovoltaics, transistors), as the reduced dispersion of surface compositions should promote a more cohesive response of nanoparticles in the film to the same chemical treatment. Based on the demonstrated homogeneity of nanocrystal shapes and the simplicity of the synthesis, we expect the present growth strategy to emerge as a viable alternative to traditional hot-injection methods of nanoparticle synthesis.

Layer-by-layer low-temperature passivation of semiconductor nanocrystals with transition metal chalcogenides

251st National Meeting (2016)

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