Soluble Metal Oxo Alkoxide Inks with Advanced Rheological Properties for Inkjet-Printed Thin-Film Transistors

Abstract

Semiconductor inks containing an indium-based oxo alkoxide precursor material were optimized regarding rheology requirements for a commercial 10 pL inkjet printhead. The rheological stability is evaluated by measuring the dynamic viscosity of the formulations for 12 h with a constant shear rate stress under ambient conditions. It is believed that the observed superior stability of the inks is the result of effectively suppressing the hydrolysis and condensation reaction between the metal oxo alkoxide precursor complex and atmospheric water. This can be attributed to a strong precursor coordination and the resulting reduction in ligand exchange dynamics of the solvent tetrahydrofurfuryl alcohol which is used as the main solvent in the formulations. It is also shown that with a proper selection of cosolvents, having high polar Hansen solubility parameter values, the inks drop formation properties and wettability can be fine-tuned by maintaining the inks rheological stability. Good drop jetting performance without satellite formation and high drop velocities of 8.25 m/s were found with the support of dimensionless numbers and printability windows. By printing single 10 pL ink dots onto short channel indium-tin-oxide electrodes, InO calcination at 350 °C and a solution-processed back-channel protection, high average saturation mobility of approximately 10 cm/(V s) are demonstrated in a bottom-contact coplanar thin-film transistor device structure.

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“…However, screen-printing requires delicate and thin screens that are tedious to manufacture. Inkjet printing of metallic ink has been widely used for high throughput, instantaneous patterning but it is sensitive to the rheological properties of ink and prone to frequent nozzle clogging 21,22 . These potential problems might be costly in resource deprived settings.…”

64‐4: Manufacturing and Encapsulation Process of Bottom Gate Bottom Contact Thin‐Film Transistors with a Printed Oxide Semiconductor

“…Obviously, the material has to fulfill many rheological requirements which ensure its printability. In this work we used a material which was specifically developed for the ink-jet printing [5]: iXsenic S (Evonik Resource Efficiency GmbH). It contains mainly an indium oxo alkoxide precursor, and different solvents which were especially added to achieve appropriate rheological properties.…”

“…This is due to the high affinity of the iXsenic material to water molecules. Indeed the formulation is developed and characterized under inert conditions [5]. In this work, the ink is stored under inert conditions, but then processed and characterized under normal atmospheric conditions.…”

Effect of Polyol Molecular Structure on Fluidity, Surface Tension, and Printed Pattern Sharpness of Disperse Dye Inks

“…4,28−30 The ink drop parameters are the basis for an evaluation of the inkjet performances. 4,28 Among these parameters, the volume, velocity, and ligament length are of a special importance to study. They have the capacity to directly affect the quality of the ink drops, thus also affecting the printing quality.…”

“…They have the capacity to directly affect the quality of the ink drops, thus also affecting the printing quality. 4,28 The ideal shape of the ink drop is spherical. Because of the ink surface tension, the ink drop itself has the tendency to automatically shrink.…”