1：Experimental Design and Method Selection:

The study focuses on the development of an ink jet printing process for ZnO semiconductor films starting from a ZnO nanoparticle formulation optimized for spin-coating. The morphological, as well as electrical, properties of spin-coated and printed ZnO layers are compared. An inkjet printed indium–tin–oxide interlayer between zinc oxide and the Ag layer is introduced to reduce the contact resistance at the metal/semiconductor interfaces.

2：Sample Selection and Data Sources:

The ZnO ink was based on a ZnO nanoparticle powder with a primary particle size of 20 nm. The ITO ink was based on a nano-sized indium tin oxide powder with a primary particle size of 19 nm.

3：List of Experimental Equipment and Materials:

ZnO nanoparticle powder (Evonik Industries AG), disperser DAS H 200-K (LAU GmbH), 3K30 centrifuge (SIGMA Laborzentrifugen GmbH), Precision Semiconductor Parameter Analyzer 4156C (Agilent), Keithley 2636 Dual Channel Source Meters.

4：Experimental Procedures and Operational Workflow:

The ZnO suspension in ethanol was dispersed with a disperser using yttrium stabilized zirconia milling beads. The dispersion was centrifuged to remove larger nanoparticle aggregates and agglomerates. The supernatant was extracted and used as ink for spin-coating. For inkjet printing, the ZnO suspension was diluted in distilled water and ethylene glycol. The ITO ink was prepared by combining the ITO powder, a solvent mixture, and a dispersing agent in a PE bottle for the dispersing procedure.

5：Data Analysis Methods:

The electrical characteristics of TFTs were measured at room temperature with a Precision Semiconductor Parameter Analyzer 4156C (Agilent) in ambient conditions or with two Keithley 2636 Dual Channel Source Meters in N atmosphere. The contact resistance between the source and drain electrode stacks and the ZnO layer was investigated using the transfer length method (TLM).