Effect of ink formulation on the inkjet printing process of Al–ZnO nanoparticles

Abstract

This study focuses on the inkjet printing of aluminum-doped zinc oxide (AZO) spherical and platelet nanoparticle-based nanoflakes with typical sizes ranging from 700 to 800 nm. The AZO nanoparticles were synthesized by aqueous precipitation. The preparation of the solvent-based inks was performed with the control of the viscosity, ink stability, and nanoparticle dispersion. The results showed that the viscosity for nanoparticle dispersions slightly changes (from 6.9 to 8.7 cPs) when the nanoparticles mass concentration increases from 1.8 to 10%. In order to achieve thin films of AZO nanoparticles, we optimized the printing process by real-time monitoring of drop velocity with a stroboscopic camera. This technology involves direct patterning of a functional material by tiny MEMS-jets on a flexible and rigid substrate at specific locations. The lowest concentration of AZO nanoparticles corresponding to 1.8% enables printing several times during the nanoparticle dispersions and the clogging of printhead nozzles is less pronounced. In our conditions, the optimum voltage value is 25 V to achieve a drop velocity from 7 to 9 m/s. In the case of nanospheres with 10% of AZO nanoparticles, for a large dropspace (90 $$\mu$$ m), the individual printed droplets appear as a sequence of linear dots. When the drop spacing decreases to 75 $$\mu$$ m, isolated drops start to overlap and merge. Further decrease in the drop spacing eliminates scalloping and leads finally to a regular and continuous layer at 55 $$\mu$$ m.