Surface Modification and Assembly of Transparent Indium Tin Oxide Nanocrystals for Enhanced Conductivity

摘要

In a solution-phase synthesis of nanocrystals (NCs), organic surfactants play an important role in size and shape control as well as in facilitating the stable dispersion of NCs in solvents. However, in order to use these NCs for electrical applications, the surfactants must be removed effectively. Here we report that monodisperse indium tin oxide (ITO) NCs were synthesized and stabilized with oleate/ oleylamine ligands, and these long-chain surfactants were readily substituted with tetrabutylammonium hydroxide (TBAOH), forming a stable methanol dispersion. Uniform assemblies of ITO NCs were made by spin-coating the ITO-TBAOH NC dispersions with an assembly thickness controllable from 68 to 260 nm by the NC solution concentration. An annealing treatment at 120 °C and 300 °C under Ar + 5% H2 for 1 h effectively removed the TBAOH, and the ITO NC assemblies showed high transparency (>88%) and low resistivity (2.6 X 10~(-3) Ω·cm). Our new approach to surface modification of ITO NCs with a volatile surfactant followed by film deposition is an effective strategy for fabricating ITO NC films by a solution process with desired transparency and conductivity for transparent electrode applications.