Study Of Inkjet Printing Organic Dielectric Material-Poly(4-vinylphenol)(PVP)and Film Characterization

In recent years, organic thin film transistor receives widespread attention in the field of flexible large area display and electronic tags. Ink-jet printing technology can directly deposit a patterned thin film, it turns out to be an effective method to pattern on flexible and large area substrates. The target of this project is to combine above two, and develop a high-performance all-printed organic thin film transistor. In view of the confidentiality requirements of active layer, this article deals only with insulating layer inkjet printing.The main work of this paper is to deposit a poly (4-vinylphenol)(PVP) insulator layer by piezoelectric inkjet printing, and to analyze factors affecting electrical properties of the thin films, the main contents include:(1) At the first beginning, we configured different concentrations of poly (4-vinylphenol)(PVP) solution, propylene glycol monomethyl ether acetate (PGMEA) used as the solvent. Analyze printability of the ink, we find out that PVP ink with concentration between4wt%and10wt%has good printability to DMP-3000printer.(2) Study relationship between PVP film morphology and ink concentration, printing drop spacing and the number of printing layers. The results show that double-layer printing can effectively reducecoffee ring phenomena, and improve uniformity of the film surface. As a thin film deposition process, inkjet printing technology can deposit a uniform insulating film with thickness in range of200～1000nm.(3) By using M-I-M structure, capacitance characteristics of the insulating layer are studied. The measurement data show that: capacitance decreases with the increase of ink concentration; increasing printing insulation layers can also decrease capacitance; and capacitance of printed PVP insulator is in nF/cm2orders of magnitude, according to published literature, it basically meets the practical requirements.(4) Studying concentrationsof PVP ink and the number of printed layersaffecting on leakage characteristics of the insulator, the leakage current tests show that: applied0-40V voltage, inkjet printed PVP films exhibit low leakage current density in the range of10-11～10-8A/cm2, as a necessary reference for printing a high performance cross-linked poly (4-vinylphenol)(CL-PVP) dielectric layer.To sum up, ink-jet printing technology can deposit high-performance organic insulating film, it is a thin film deposition technology available for the field of Organic Electronics Manufacturing.