Electrical Resistivity of Assembled Transparent Inorganic Oxide Nanoparticle Thin Layers: Influence of Silica, Insulating Impurities, and Surfactant Layer Thickness

Abstract

Transparent, conductive layers prepared from nanoparticle dispersion of doped oxides are highly sensitive to impurities. Currently investigated cost efficient and fast production of thin conducting films for use in consumer electronics relies on wet processing such as spin and/or dip coating of surfactant-stabilized nanoparticle dispersions. This inherently results in entrainment of organic and inorganic impurities into the conducting layer leading to largely varying electrical conductivity. Therefore this study provides a systematic investigation on the effect of insulating surfactants, small organic molecules and silica in terms of pressure dependent electrical conductivity as a result of different core/shell structure (layer thickness). Application of high temperature flame synthesis gives access to antimony-doped tin oxide (ATO) nanoparticles with high purity. This well-defined starting material was then subjected to representative film preparation processes using organic additives. In addition ATO nanoparticles were prepared with a homogeneous inorganic silica layer (silica layer thickness from 0.7 to 2 nm). Testing both organic and inorganic shell materials for the electronic transport through the nanoparticle composite allowed a systematic study on the influence of surface adsorbates (e.g. organic, insulating materials on the conducting nanoparticle's surface) in comparison to well-known insulators such as silica. Insulating impurities or shells revealed a dominant influence of tunneling effect on the overall layer resistance. Mechanical relaxation phenomena were found for 2 nm insulating shells for both large polymer surfactants and (inorganic) SiO 2 shells.

Polyol synthesized aluminum doped zinc oxide nanoparticles - influence of the hydration ratio on crystal growth, dopant incorporation and electrical properties

“…To investigate the electrical properties of the bulk material, we measured the resistance with a two-point measurement setup as described from Pluemel [36] or Bubenhofer et al [15]. To ensure a dense packing of the particles, the measurements were carried out with a pressure of 3.7x10 3 bar.…”

“…That can be ascribed to higher porosities (lower density) and a big amount of grain boundaries that hinder the electron transfer from particle to particle and therefore through the coating [10,11,12,13]. To prepare particle coatings with adequate properties, stable nanoparticle dispersions or inks with low-agglomerated, conductive nanoparticles are necessary [14,15]. With the help of crystalline solution processed nanoparticles and different additives and stabilizers it is possible to prepare low agglomerated particle suspensions to guarantee a good arrangement of the particles on a substrate [16,17].…”

Porous and Transparent Metal‐oxide Electrodes : Preparation Methods and Electroanalytical Application Prospects

“…Bubenhofer et al . have also studied similar films and their interactions with various non‐conductive coatings to simulate a resistance increase with environmentally‐sourced impurities . A simple protocol of casting the ATO nanoparticle dispersion was developed by Guo et al .…”

Boosting Electrochemical Activity of Porous Transparent Conductive Oxides Electrodes Prepared by Sequential Infiltration Synthesis

“…Numerous approaches have been proposed for the fabrication of porous transparent electrodes, including nanoparticle casting, [ 18,19 ] salt precursor deposition, [ 20,21 ] etching, [ 19,22 ] and electrospinning. [ 23 ] Casting a nanoparticle via dip coating or spin coating is a low‐cost, simple method to prepare porous TCOs.…”