Economical Flexible Electronics Incorporating All-Solution-Processed Transistors on Paper

Paper electronics is receiving great interest because it is one of the best candidates for next-generation devices with many useful features such as low cost, disposability, and flexibility. However, the rough and porous surface of standard paper accelerates the spreading of liquid ink, limiting the manufacture of solution-processed paper electronics. Here, we use extremely rough and absorptive paper substrate without any treatment with an overall average RMS roughness much higher than that of general-purpose paper. The AgNW network acting as a gate electrode was formed on the paper surface by absorbing the AgNW solution (1 wt% in DI water) into the filter paper using a home-made screen printer screen printed gate electrode with low sheet resistance (9±5 Ω/sq) and low root mean square (RMS) roughness of 130±10 nm was obtained after drying for 30 min under ambient air without heating treatment. Then, the PVDF-HFP (Poly(vinylidene fluoride-co-hexafluoropropylene)) solution (20 wt% dissolved in DMF (N, N-Dimethylmethanamide)) is injected onto the surface by screen printing. In the vacuum state at a pressure of 0.002 atm for 5 min, a certain amount of PVDF-HFP solution is filtered in the AgNWs network layer and most of the solution is absorbed. As a result, a dielectric layer of less than 10 µm is cured thinly on the surface of the AgNW-assembled paper. The solution-processed flexible FETs on paper exhibit electrical performance with charge carrier mobility of 0.053 cm² V^-1 s^-1, and a current on/off ratio of 7×10². We report the development of zinc oxide nanowire (ZnO NW) field-effect transistors (FETs) on paper with facile, low-cost, and large-area manufacturing. By utilizing simple equipment such as a vacuum filter and a homemade pulling system, we could produce outstanding FETs that are desirable for cheap flexible electronic applications.