Advances in synthetic methods allow a wide range of semiconductor, metal, and metal-oxide nanocrystals (NCs) to be tailored in size and shape and to be used as building blocks in the design of NC solids. However, the long, insulating ligands commonly employed in the synthesis of colloidal NCs inhibit strong interparticle coupling and charge transport once NCs are assembled into the solid state as NC arrays. We introduce short, compact ligands to exchange the long, insulating ligands used in synthesis and increase interparticle coupling. In semiconductor NCs, the strong interparticle coupling leads to red-shifts in the optical absorption and concomitant increases in carrier mobilities. Doping of the NC thin films is used to control the carrier statistics, shift the Fermi energy, and fill traps. I will give examples where semiconductor NC solid design is used to realize high mobility n- and p-type materials for field-effect transistors and integrated circuits and for solar photovoltaics. In metal NCs, chemically-controlled coupling allows us to tailor a dielectric-to-metal phase transition seen by a 1010 range in DC conductivity and a dielectric permittivity ranging from everywhere positive to everywhere negative across the whole range of optical frequencies. The compact ligand allow us to realize a 'diluted metal' with optical properties akin to next-generation metamaterials. I will show we can harness the properties of metal NCs by using nanoimprint lithography to print large-area metamaterials on glass and plastics with widely tailorable optical properties.

Designer materials through controlled nanocrystal coupling for electronic and optical applications

248th National Meeting (2014)

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