Conductivity and adhesion enhancement in low-temperature processed indium tin oxide/polymer nanocomposites

We report on the conductivity and adhesion enhancement of indium tin oxide (In2O3:Sn; ITO) nanoparticle films by the application of polymers as matrix material. We fabricated ITO layers at a maximum process temperature of 130 degrees C by modifying and spin-coating nanoparticulate ITO dispersions. Dispersions containing the organic film-forming agent polyvinylpyrrolidone (PVP) and the organofunctional coupling agent 3-methacryloxypropyltrimethoxysilane (MPTS) have been developed to obtain transparent and conducting coatings on substrates which do not withstand high process temperatures like polymers or already processed glasses. The layers were cured by UV-irradiation as well as by low-temperature heat treatment (T = 130 degrees C) in air and under forming gas atmosphere (N-2/H-2). The influence of the additives on the electrical, optical, morphological and mechanical layer properties is reported. Compared to best pure ITO layers (3.1 Omega(-1)cm(-1)), the ITO-MPTS-PVP nanocomposite coatings exhibit a conductance of 9.8 Omega(-1)cm(-1). Stable sheet resistances of 750 Omega/square at a coexistent transmittance of 86% at 550 nm for a layer thickness of about 1.3 mu m were achieved. The conductance enhancement is a consequence of the consolidation of the ITO nanoparticle network due to the acting shrinkage forces caused either by drying in the case of PVP or UV-irradiation induced condensation and polymerization reactions in the case of MPTS. (C) 2009 Elsevier B.V. All rights reserved.