Development of indium tin oxide (ITO) nanoparticle incorporated transparent conductive oxide thin films

Yavaş, Hakan
Indium tin oxide (ITO) thin films have been used as transparent electrodes in many technological applications such as display panels, solar cells, touch screens and electrochromic devices. Commercial grade ITO thin films are usually deposited by sputtering. Solution-based coating methods, such as sol-gel however, can be simple and economic alternative method for obtaining oxide films and also ITO. In this thesis, “ITO sols” and “ITO nanoparticle-incorporated hybrid ITO coating sols” were prepared using indium chloride (InCl34H2O) or indium nitrate (InNO3•xH2O) and tin nitrate (SnCl45H2O) precursors in order to form transparent conductive films on glass. The specific objectives of the study were two-fold. The first objective was to investigate the effect of sol-gel processing variables; heat treatment temperature (350º-600 ºC), spin coating process parameters (rate and time), number of coating operations (1, 2, 4, 7 and 10 layers) and sol aging on the electrical/optical/microstructural properties of ITO thin films (plain ITO thin films). The results showed that, highly transparent (97 % in the visible region) and moderately conductive (1.2 kΩ/sqr) ITO thin films can be obtained after calcination in air at 550 ºC by optimization of the coating sol concentration. The surface coverage and thickness of thin films can be controlled by spin rate-time and number of coatings. In addition, it was found that, induce-aging (at temperatures < 100 °C, for several hours) of the premature coating sol prior to deposition can be a practical tool for controlling/modifying the physical properties of the plain ITO films. In the second part of the study, the effect of nanoparticle incorporation into the ITO sols at different extent on optoelectronic and microstructural properties of ITO thin films were reported (hybrid ITO thin films). Initially, parametric colloidal chemistry studies were performed in defining the conditions for obtaining stable ITO suspensions that can incorporated into the ITO sol. Then, the reasons and structural/chemical controlling factors leading to improvements in the functional properties for these hybrid films are presented and thoroughly discussed, compared to the properties of their plain (unmodified) counterparts.