Size-tunable optical properties and the ability to process thin films using scalable, cost-efficient printing techniques have long made colloidal nanocrystals (NCs) an attractive candidate for next-generation optoelectronics. Much of the recent progress in this direction hinges on the ability to manipulate the NC surface. Conventional solution synthesis yields NCs with ligands bound to metal surface atoms through a labile acid-base complex. The electrically-insulating native ligands are thus routinely exchanged to produce conductive NC arrays for devices such as solar cells, light-emitting devices, transistors, and photodetectors. Just as surface manipulation has launched metal-based NCs to the forefront of optoelectronic technology, it is the inability to do so with the covalent surface of group IV NCs that has greatly hindered progress. In this work, we demonstrate a Lewis acidic boron surface chemistry of gas-phase synthesized Si NCs that provides the same solution-phase versatility as their metal-based counterparts. This represents an immense step toward an abundant, non-toxic alternative to Pb and Cd-based NCs. These Si NCs are also uniquely suited for investigating the mechanism of colloidal stability that has been observed after metal-based NCs are stripped of ligands or ligand-exchanged for ionic ligands. We find the electrostatic mechanism previously invoked to be incomplete. An alternative model is proposed from which we demonstrate stable Si NC colloids in media that runs the gamut from hexane to water.

Interface engineering for nanocrystal stability in media spanning hexane to water

249th National Meeting (2015)

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