Dispersion stability of AZO nanocrystals concerning their processing into functional thin films using small angle X-ray scattering (SAXS)
The semiconductor aluminum-doped zinc oxide (AZO) has versatile applications due to its special properties, e.g. low electrical resistance and a high degree of transparency in the visible range. Due to these properties AZO will be considered to be a significant cheaper alternative in order to replace existing and finite indium based oxides for diverse scopes e.g. thin-film solar modules, touch-panels, light-emitting diodes or printing electronics. The preparation of high-performance AZO thin films requires stable starting dispersions of high-quality AZO nanocrystals with tailored crystal shapes and sizes as well as a defined Al doping to set specific application properties. This research project has already developed a fundamental understanding of the growth process of tailor-made AZO nanocrystals (x_50<50nm) during their liquid-phase synthesis and their impact parameters using X-ray-based on-line analysis techniques . In view of the planned production of homogeneous thin films from stabilized AZO nanocrystal starting dispersions, a suitable stabilization process on the primary particle level for AZO is to be developed on the basis of the knowledge gained so far. The focus of the analyzes concerning the individual process steps and their subsequent linking (synthesis -> stabilization -> coating) is the small angle X-ray scattering (SAXS) as a non-invasive particle measurement technique using our SAXS laboratory camera. As part of the development of a stabilization process, investigations are planned on the stabilization efficiency of n-carboxylic acid stabilizers, the time-resolved analyzes of dispersion stability (e.g., sedimentation analysis) and the characterization of particle properties (e.g., size, fractal properties, etc.) of the starting AZO dispersions using SAXS. In this contribution an adaptation of the particle system to our lab-scale SAXS measurement system by means of appropriate sample preparation techniques, special features of the instrumental set-up and a comprehensive investigation about dispersion stability of the AZO nanocrystal starting dispersions at the nanoscale range of 10-75 nm, dependent on stabilization parameters, will be reported in detail.
 J. Ungerer, A.-K. Thurm, M. Meier, M. Klinge, G. Garnweitner, and H. Nirschl, “Development of a growth model for aluminum-doped zinc oxide nanocrystal synthesis via the benzylamine route,” Journal of Nanoparticle Research, vol. 21, no. 5, pp. 106, May 23, 2019.