Synthesis of a Nonagglomerated Indium Tin Oxide Nanoparticle Dispersion

The importance and use of transparent conducting oxides (TCOs) has grown significantly over the last decade. The most successful of these materials is tin-doped indium oxide (ITO), which can be found in a wide variety of applications including flat-panel displays, functional glass, solar cells, and lightemitting diodes. When deposited as a thin film, the conductivity of an ITO layer commonly reaches 1000 S cm 1 with >80% optical transmittance in the visible spectral region. This thin film form has traditionally been achieved using sputtering approaches that require annealing and sintering steps in excess of 700 8C for crystallization and conductivity enhancement. Accordingly, sputtered films have been restricted to somewhat flat substrates, and to materials that can withstand high annealing temperatures. In response, research into the production and use of ITO nanoparticles has steadily increased over the last few years. It is expected that highly crystalline particles, with an average diameter of less than 10 nm, will sinter at lower temperatures, and thus, allow broader application to complex geometries, heat-sensitive materials, and flexible substrates. Additionally, recent interest in applying ink-jet printing technology to ITO deposition has further expanded the need for a nanoparticle form that displays high crystallinity with nonagglomeration in solution. Although some low-temperature co-precipitation synthetic techniques have produced nanometer-sized particles, the need for a high-temperature (500 8C) crystallization step typically resulted in widespread particle agglomeration. Solvothermal and microwave-assisted synthesis of ITO has been successful in forming small and crystalline particles that do not require any high-temperature annealing. However, some agglomeration is still present. In essence, the type of ITOnanoparticle system desired is one thatmirrors themorphology of typical colloidal quantum dots (QDs). The intricate size–